feat(restaurant): cart store + cart page + add-to-cart wiring

stores/cart.ts — Pinia store keyed by restaurant_id (multi-
restaurant ready for the festival aggregator,
aiolabs/restaurant#8, without schema changes). Persists to
STORAGE_SERVICE under 'restaurant.cart.v1' (debounced 200ms);
hydrates on creation. Money is integer msat-ish (the cart stores
unit_msat as the per-unit value pulled from MenuItem.price; the
buildCreateOrder helper in commit 6 owns the canonical msat
conversion at order-place time).

  State: { lines: Record<restaurant_id, CartLine[]>,
           activeRestaurantId: string | null }
  Lines that match item + modifier set + note merge into the
  same line with quantity++ rather than duplicating.

Getters: restaurantsInCart, itemCount, restaurantTotalsMsat,
grandTotalMsat, linesFor(rid).

Actions: addLine, setQty, incrementQty, decrementQty, removeLine,
clearRestaurant, clear, setActiveRestaurant.

components/CartLineItem.vue — single line with modifier summary,
qty stepper, note display, remove button.

views/CartPage.vue — lines grouped by restaurant. Multi-restaurant
display already works (each restaurant is its own card). Empty
state, subtotal, clear-cart, Checkout CTA (lands in commit 6).

Wiring:
  - ItemPage 'Add to cart' now actually adds, then routes to /cart.
  - RestaurantPage's quick-add (the '+' on cards with NO modifier
    groups) adds directly without opening ItemPage; cards WITH
    modifier groups still open the detail page so the customer
    can satisfy required choices.
  - App.vue bottom-nav 'Cart' badge reflects cart.itemCount.
  - New route /cart registered on the module.

Verified: vue-tsc -b clean.

src/modules/restaurant/components/CartLineItem.vue

@@ -0,0 +1,97 @@
+<script setup lang="ts">
+/**
+ * Single line in the cart: name, modifier summary, qty stepper,
+ * remove button.
+ */
+import { computed } from 'vue'
+import { Plus, Minus, Trash2 } from 'lucide-vue-next'
+import { Button } from '@/components/ui/button'
+import type { CartLine } from '../stores/cart'
+
+const props = defineProps<{
+  line: CartLine
+  currencyHint?: string
+}>()
+
+const emit = defineEmits<{
+  (e: 'increment'): void
+  (e: 'decrement'): void
+  (e: 'remove'): void
+}>()
+
+const modifierSummary = computed(() =>
+  props.line.selected_modifiers.map((m) => m.name).join(' · ')
+)
+
+const lineTotal = computed(() => {
+  // unit_msat is base + modifier delta snapshot; the cart store
+  // currently stores it as a sat-major number (price * 1000-less
+  // because the extension's `price` is already in the declared
+  // currency, not msat — see useCheckout's buildCreateOrder for the
+  // canonical conversion at order-place time).
+  const fmt = new Intl.NumberFormat(undefined, { maximumFractionDigits: 2 })
+  const total = props.line.unit_msat * props.line.quantity
+  return `${fmt.format(total)} ${props.currencyHint || 'sat'}`
+})
+</script>
+
+<template>
+  <li class="flex items-stretch gap-3 rounded-xl border border-border bg-card p-3">
+    <div class="min-w-0 flex-1">
+      <div class="flex items-start justify-between gap-2">
+        <h4 class="line-clamp-1 font-semibold text-foreground">
+          {{ line.name }}
+        </h4>
+        <span class="shrink-0 font-mono text-sm text-primary">
+          {{ lineTotal }}
+        </span>
+      </div>
+      <p
+        v-if="modifierSummary"
+        class="mt-1 line-clamp-2 text-xs text-muted-foreground"
+      >
+        {{ modifierSummary }}
+      </p>
+      <p
+        v-if="line.note"
+        class="mt-1 line-clamp-2 text-xs italic text-muted-foreground"
+      >
+        Note: {{ line.note }}
+      </p>
+      <div class="mt-2 flex items-center gap-2">
+        <div class="inline-flex items-center rounded-full border border-border bg-background">
+          <Button
+            variant="ghost"
+            size="icon"
+            class="h-7 w-7 rounded-full"
+            aria-label="Decrease quantity"
+            @click="emit('decrement')"
+          >
+            <Minus class="h-3.5 w-3.5" />
+          </Button>
+          <span class="w-7 text-center font-mono text-sm" aria-live="polite">
+            {{ line.quantity }}
+          </span>
+          <Button
+            variant="ghost"
+            size="icon"
+            class="h-7 w-7 rounded-full"
+            aria-label="Increase quantity"
+            @click="emit('increment')"
+          >
+            <Plus class="h-3.5 w-3.5" />
+          </Button>
+        </div>
+        <Button
+          variant="ghost"
+          size="icon"
+          class="h-7 w-7 text-destructive hover:text-destructive"
+          aria-label="Remove line"
+          @click="emit('remove')"
+        >
+          <Trash2 class="h-3.5 w-3.5" />
+        </Button>
+      </div>
+    </div>
+  </li>
+</template>

src/modules/restaurant/index.ts

@@ -88,6 +88,12 @@ export const restaurantModule: ModulePlugin = {
       component: () => import('./views/ItemPage.vue'),
       meta: { requiresAuth: false, title: 'Item' },
     },
+    {
+      path: '/cart',
+      name: 'restaurant-cart',
+      component: () => import('./views/CartPage.vue'),
+      meta: { requiresAuth: false, title: 'Cart' },
+    },
   ] as RouteRecordRaw[],
 }
 

src/modules/restaurant/stores/cart.ts

@@ -0,0 +1,230 @@
+/**
+ * Restaurant cart store (Pinia).
+ *
+ * Multi-restaurant ready by design — `lines` is keyed by
+ * `restaurant_id`. v1 only exercises the single-restaurant path
+ * (URL-driven /r/:slug), but the festival aggregator
+ * (aiolabs/restaurant#8) lands on top of this same store with
+ * **zero schema changes** — it just adds lines from more restaurants.
+ *
+ * Persistence: state is mirrored to STORAGE_SERVICE under
+ * `restaurant.cart.v1` (debounced). Re-hydrated on store creation.
+ * Money is integer **msat** end-to-end (matches the extension).
+ */
+
+import { computed, watch } from 'vue'
+import { defineStore } from 'pinia'
+import { ref } from 'vue'
+import { tryInjectService, SERVICE_TOKENS } from '@/core/di-container'
+import type { StorageService } from '@/core/services/StorageService'
+import type { SelectedModifier } from '../types/restaurant'
+
+const STORAGE_KEY = 'restaurant.cart.v1'
+
+export interface CartLine {
+  /** UUID for dedup of identical items + modifier sets. */
+  line_id: string
+  restaurant_id: string
+  restaurant_slug: string
+  menu_item_id: string
+  /** Snapshot at add-time so the cart still renders if the menu
+   *  item is later edited / deleted. */
+  name: string
+  /** Base price + selected modifier deltas, in msat. */
+  unit_msat: number
+  quantity: number
+  selected_modifiers: SelectedModifier[]
+  note?: string | null
+}
+
+export interface CartState {
+  lines: Record<string, CartLine[]>
+  activeRestaurantId: string | null
+}
+
+const blank: CartState = { lines: {}, activeRestaurantId: null }
+
+function uuid(): string {
+  // crypto.randomUUID is available in modern browsers + Node 19+.
+  if (typeof crypto !== 'undefined' && 'randomUUID' in crypto) {
+    return crypto.randomUUID()
+  }
+  return `line-${Date.now()}-${Math.random().toString(36).slice(2, 10)}`
+}
+
+/** Two lines are merge-equivalent iff same item + same modifier set
+ *  + same note. Modifier id sort gives an order-independent compare. */
+function modifierKey(mods: SelectedModifier[]): string {
+  return mods
+    .map((m) => m.modifier_id ?? m.name)
+    .filter(Boolean)
+    .sort()
+    .join('|')
+}
+
+export const useCartStore = defineStore('restaurant-cart', () => {
+  const storage = tryInjectService<StorageService>(
+    SERVICE_TOKENS.STORAGE_SERVICE
+  )
+
+  // Hydrate from persistence (if available).
+  const initial = storage?.getUserData<CartState>(STORAGE_KEY, blank) ?? blank
+
+  const lines = ref<Record<string, CartLine[]>>(
+    structuredClone(initial.lines || {})
+  )
+  const activeRestaurantId = ref<string | null>(
+    initial.activeRestaurantId ?? null
+  )
+
+  // -------------------------- getters --------------------------------
+
+  const restaurantsInCart = computed<string[]>(() =>
+    Object.keys(lines.value).filter((rid) => lines.value[rid].length > 0)
+  )
+
+  const itemCount = computed<number>(() => {
+    let n = 0
+    for (const rid of Object.keys(lines.value)) {
+      for (const l of lines.value[rid]) n += l.quantity
+    }
+    return n
+  })
+
+  const restaurantTotalsMsat = computed<Record<string, number>>(() => {
+    const out: Record<string, number> = {}
+    for (const rid of Object.keys(lines.value)) {
+      out[rid] = lines.value[rid].reduce(
+        (s, l) => s + l.unit_msat * l.quantity,
+        0
+      )
+    }
+    return out
+  })
+
+  const grandTotalMsat = computed<number>(() =>
+    Object.values(restaurantTotalsMsat.value).reduce((s, v) => s + v, 0)
+  )
+
+  function linesFor(restaurantId: string): CartLine[] {
+    return lines.value[restaurantId] || []
+  }
+
+  // -------------------------- actions --------------------------------
+
+  function setActiveRestaurant(restaurantId: string | null): void {
+    activeRestaurantId.value = restaurantId
+  }
+
+  function addLine(line: Omit<CartLine, 'line_id'>): CartLine {
+    const bucket = (lines.value[line.restaurant_id] ||= [])
+    const myKey = modifierKey(line.selected_modifiers)
+    const existing = bucket.find(
+      (l) =>
+        l.menu_item_id === line.menu_item_id &&
+        modifierKey(l.selected_modifiers) === myKey &&
+        (l.note ?? '') === (line.note ?? '')
+    )
+    if (existing) {
+      existing.quantity += line.quantity
+      return existing
+    }
+    const newLine: CartLine = { line_id: uuid(), ...line }
+    bucket.push(newLine)
+    if (!activeRestaurantId.value) {
+      activeRestaurantId.value = line.restaurant_id
+    }
+    return newLine
+  }
+
+  function setQty(restaurantId: string, lineId: string, qty: number): void {
+    const bucket = lines.value[restaurantId]
+    if (!bucket) return
+    const line = bucket.find((l) => l.line_id === lineId)
+    if (!line) return
+    if (qty <= 0) {
+      removeLine(restaurantId, lineId)
+      return
+    }
+    line.quantity = qty
+  }
+
+  function incrementQty(restaurantId: string, lineId: string): void {
+    const bucket = lines.value[restaurantId]
+    if (!bucket) return
+    const line = bucket.find((l) => l.line_id === lineId)
+    if (line) line.quantity++
+  }
+
+  function decrementQty(restaurantId: string, lineId: string): void {
+    const bucket = lines.value[restaurantId]
+    if (!bucket) return
+    const line = bucket.find((l) => l.line_id === lineId)
+    if (!line) return
+    if (line.quantity <= 1) {
+      removeLine(restaurantId, lineId)
+    } else {
+      line.quantity--
+    }
+  }
+
+  function removeLine(restaurantId: string, lineId: string): void {
+    const bucket = lines.value[restaurantId]
+    if (!bucket) return
+    lines.value[restaurantId] = bucket.filter((l) => l.line_id !== lineId)
+    if (lines.value[restaurantId].length === 0) {
+      delete lines.value[restaurantId]
+      if (activeRestaurantId.value === restaurantId) {
+        activeRestaurantId.value = restaurantsInCart.value[0] ?? null
+      }
+    }
+  }
+
+  function clearRestaurant(restaurantId: string): void {
+    delete lines.value[restaurantId]
+    if (activeRestaurantId.value === restaurantId) {
+      activeRestaurantId.value = restaurantsInCart.value[0] ?? null
+    }
+  }
+
+  function clear(): void {
+    lines.value = {}
+    activeRestaurantId.value = null
+  }
+
+  // -------------------------- persistence ----------------------------
+
+  let writeTimer: ReturnType<typeof setTimeout> | null = null
+  function persist(): void {
+    if (!storage) return
+    if (writeTimer) clearTimeout(writeTimer)
+    writeTimer = setTimeout(() => {
+      storage.setUserData<CartState>(STORAGE_KEY, {
+        lines: lines.value,
+        activeRestaurantId: activeRestaurantId.value,
+      })
+    }, 200)
+  }
+  watch([lines, activeRestaurantId], persist, { deep: true })
+
+  return {
+    // state
+    lines,
+    activeRestaurantId,
+    // getters
+    restaurantsInCart,
+    itemCount,
+    restaurantTotalsMsat,
+    grandTotalMsat,
+    linesFor,
+    // actions
+    setActiveRestaurant,
+    addLine,
+    setQty,
+    incrementQty,
+    decrementQty,
+    removeLine,
+    clearRestaurant,
+    clear,
+  }
+})

src/modules/restaurant/views/CartPage.vue

@@ -0,0 +1,118 @@
+<script setup lang="ts">
+/**
+ * Cart review. v1 shows lines grouped by restaurant (multi-
+ * restaurant ready — single bucket today). "Checkout" jumps to
+ * /checkout where useCheckout runs the place-order + bolt11 pay
+ * sequence (commit 6).
+ */
+import { computed } from 'vue'
+import { useRouter } from 'vue-router'
+import { ArrowLeft, ShoppingCart } from 'lucide-vue-next'
+import { Alert, AlertTitle, AlertDescription } from '@/components/ui/alert'
+import { Button } from '@/components/ui/button'
+import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
+import { Separator } from '@/components/ui/separator'
+import CartLineItem from '../components/CartLineItem.vue'
+import { useCartStore } from '../stores/cart'
+
+const router = useRouter()
+const cart = useCartStore()
+
+const buckets = computed(() =>
+  cart.restaurantsInCart.map((rid) => ({
+    restaurantId: rid,
+    // restaurant_slug comes from the line snapshot so we don't need
+    // a separate fetch for the cart page header.
+    restaurantSlug: cart.linesFor(rid)[0]?.restaurant_slug ?? '',
+    lines: cart.linesFor(rid),
+    totalMsat: cart.restaurantTotalsMsat[rid] ?? 0,
+  }))
+)
+
+function fmtSat(value: number): string {
+  return `${new Intl.NumberFormat(undefined, { maximumFractionDigits: 2 }).format(value)} sat`
+}
+</script>
+
+<template>
+  <main class="container mx-auto max-w-2xl px-4 pb-24 pt-3 sm:py-6">
+    <Button variant="ghost" size="sm" class="mb-3" @click="router.back()">
+      <ArrowLeft class="mr-2 h-4 w-4" />
+      Back
+    </Button>
+
+    <header class="mb-4 flex items-baseline justify-between">
+      <h1 class="text-2xl font-bold text-foreground">Cart</h1>
+      <span class="text-sm text-muted-foreground">
+        {{ cart.itemCount }} item{{ cart.itemCount === 1 ? '' : 's' }}
+      </span>
+    </header>
+
+    <Alert v-if="!buckets.length" class="border-border">
+      <ShoppingCart class="h-4 w-4" />
+      <AlertTitle>Your cart is empty</AlertTitle>
+      <AlertDescription>
+        Browse a menu and tap “+” to add items.
+      </AlertDescription>
+    </Alert>
+
+    <template v-else>
+      <div class="space-y-4">
+        <Card v-for="b in buckets" :key="b.restaurantId">
+          <CardHeader class="flex flex-row items-baseline justify-between space-y-0">
+            <CardTitle class="text-base">
+              <button
+                type="button"
+                class="text-left text-foreground hover:text-primary"
+                @click="router.push(`/r/${b.restaurantSlug}`)"
+              >
+                {{ b.restaurantSlug }}
+              </button>
+            </CardTitle>
+            <span class="font-mono text-sm text-primary">
+              {{ fmtSat(b.totalMsat) }}
+            </span>
+          </CardHeader>
+          <CardContent>
+            <ul class="space-y-2">
+              <CartLineItem
+                v-for="line in b.lines"
+                :key="line.line_id"
+                :line="line"
+                @increment="cart.incrementQty(b.restaurantId, line.line_id)"
+                @decrement="cart.decrementQty(b.restaurantId, line.line_id)"
+                @remove="cart.removeLine(b.restaurantId, line.line_id)"
+              />
+            </ul>
+          </CardContent>
+        </Card>
+      </div>
+
+      <Separator class="my-6" />
+
+      <div class="space-y-3">
+        <div class="flex items-center justify-between">
+          <span class="text-sm text-muted-foreground">Subtotal</span>
+          <span class="font-mono text-lg font-semibold text-foreground">
+            {{ fmtSat(cart.grandTotalMsat) }}
+          </span>
+        </div>
+        <Button
+          class="w-full"
+          size="lg"
+          :disabled="!buckets.length"
+          @click="router.push('/checkout')"
+        >
+          Checkout
+        </Button>
+        <Button
+          variant="ghost"
+          class="w-full text-destructive hover:text-destructive"
+          @click="cart.clear()"
+        >
+          Clear cart
+        </Button>
+      </div>
+    </template>
+  </main>
+</template>

src/modules/restaurant/views/ItemPage.vue

@@ -15,6 +15,7 @@ import { Button } from '@/components/ui/button'
 import { Textarea } from '@/components/ui/textarea'
 import ModifierSelector from '../components/ModifierSelector.vue'
 import { useMenu } from '../composables/useMenu'
+import { useCartStore } from '../stores/cart'
 import type {
   EnrichedMenuItem,
   SelectedModifier,
@@ -22,6 +23,7 @@ import type {
 
 const route = useRoute()
 const router = useRouter()
+const cart = useCartStore()
 
 const slug = computed(() => String(route.params.slug || ''))
 const itemId = computed(() => String(route.params.itemId || ''))
@@ -74,16 +76,23 @@ function decrement() {
   if (quantity.value > 1) quantity.value--
 }
 
-// Cart store is added in commit 5 — placeholder for now.
 const canAdd = computed(
   () => !!item.value && !isSoldOut.value && modifiersValid.value
 )
 
 function addToCart() {
-  // Wired in commit 5.
-  console.warn(
-    '[restaurant] Cart store not yet wired — commit 5 adds this.'
-  )
+  if (!item.value || !restaurant.value) return
+  cart.addLine({
+    restaurant_id: restaurant.value.id,
+    restaurant_slug: restaurant.value.slug,
+    menu_item_id: item.value.id,
+    name: item.value.name,
+    unit_msat: unitPrice.value,
+    quantity: quantity.value,
+    selected_modifiers: selectedModifiers.value,
+    note: note.value || null,
+  })
+  router.push('/cart')
 }
 
 function back() {

src/modules/restaurant/views/RestaurantPage.vue

@@ -20,9 +20,11 @@ import RestaurantHeader from '../components/RestaurantHeader.vue'
 import CategoryNav from '../components/CategoryNav.vue'
 import MenuTree from '../components/MenuTree.vue'
 import { useMenu } from '../composables/useMenu'
+import { useCartStore } from '../stores/cart'
 
 const route = useRoute()
 const router = useRouter()
+const cart = useCartStore()
 
 const slug = computed(() => String(route.params.slug || ''))
 const { restaurant, tree, items, isLoading, error, refresh } = useMenu(
@@ -33,11 +35,28 @@ function openItem(itemId: string) {
   router.push(`/r/${slug.value}/item/${itemId}`)
 }
 
-// "Quick-add" is forwarded by MenuItemCard when an item has no
-// modifier groups. Cart store lands in commit 5 — until then it
-// behaves the same as opening the item detail.
+/**
+ * Quick-add bypasses ItemPage for items that have no modifier groups.
+ * Items with modifier groups always route through ItemPage so the
+ * customer can pick required options before the line is added.
+ */
 function quickAdd(itemId: string) {
-  openItem(itemId)
+  const it = items.value.find((i) => i.id === itemId)
+  if (!it || !restaurant.value) return
+  if (it.modifier_groups.length > 0) {
+    openItem(itemId)
+    return
+  }
+  cart.addLine({
+    restaurant_id: restaurant.value.id,
+    restaurant_slug: restaurant.value.slug,
+    menu_item_id: it.id,
+    name: it.name,
+    unit_msat: it.price,
+    quantity: 1,
+    selected_modifiers: [],
+    note: null,
+  })
 }
 </script>
 

src/restaurant-app/App.vue

@@ -4,13 +4,14 @@ import { useRoute } from 'vue-router'
 import { Utensils, ShoppingCart, ReceiptText } from 'lucide-vue-next'
 import AppShell from '@/components/layout/AppShell.vue'
 import type { BottomTab } from '@/components/layout/BottomNav.vue'
+import { useCartStore } from '@/modules/restaurant/stores/cart'
 
 const route = useRoute()
+const cart = useCartStore()
 
-// The cart store hooks in during commit 5; v1 skeleton renders the
-// badge as null. Bottom-nav lives in AppShell and works fine with
-// zero badge values.
-const cartItemCount = computed<number | null>(() => null)
+const cartItemCount = computed<number | null>(() =>
+  cart.itemCount > 0 ? cart.itemCount : null
+)
 
 const tabs = computed<BottomTab[]>(() => [
   { name: 'Browse', icon: Utensils, path: '/' },