feat(restaurant/checkout): tag outgoing payment with restaurant + order id

Adds extra={tag:'restaurant', restaurant_id, order_id} to the
POST /api/v1/payments body when paying a placed-order's bolt11.
Mirrors the same extras the extension stamps on its incoming
invoice, so a customer's wallet history can later filter or
surface restaurant orders rather than showing them as generic
Lightning sends.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/modules/restaurant/composables/useCheckout.ts

@@ -236,7 +236,8 @@ export function useCheckout(): UseCheckoutReturn {
 
   async function payBolt11Raw(
     bolt11: string,
-    adminkey: string
+    adminkey: string,
+    extra?: Record<string, unknown>
   ): Promise<void> {
     const response = await fetch(`${apiBaseUrl}/api/v1/payments`, {
       method: 'POST',
@@ -244,7 +245,7 @@ export function useCheckout(): UseCheckoutReturn {
         'Content-Type': 'application/json',
         'X-Api-Key': adminkey,
       },
-      body: JSON.stringify({ out: true, bolt11 }),
+      body: JSON.stringify({ out: true, bolt11, ...(extra ? { extra } : {}) }),
     })
     if (!response.ok) {
       let detail = response.statusText
@@ -272,7 +273,15 @@ export function useCheckout(): UseCheckoutReturn {
     state.value.step = 'paying'
     state.value.currentRestaurantSlug = placed.restaurantSlug
     try {
-      await payBolt11Raw(placed.invoice.bolt11, adminkey)
+      // Tag the outgoing payment so the customer's wallet history
+      // can later surface it as a restaurant order. Mirrors the
+      // `extra={"tag": "restaurant", ...}` the extension stamps on
+      // its incoming invoice.
+      await payBolt11Raw(placed.invoice.bolt11, adminkey, {
+        tag: 'restaurant',
+        restaurant_id: placed.restaurantId,
+        order_id: placed.order.id,
+      })
       // Set semantics keeps `paidOrderIds` from re-renders; rebuild
       // it on update so Vue picks up the change.
       state.value.paidOrderIds = new Set([