feat(activities): parse ticket inventory tags from NIP-52 events

The aiolabs/events extension publishes six AIO custom tags on every
kind 31922/31923 calendar event (tickets_available, _sold, _price,
_currency, _allow_fiat, _fiat_currency — see aiolabs/events#15) and
republishes the event on every ticket sale. Connected clients pick
up the new state via their existing relay subscription, no REST
polling.

- New TicketTags shape on CalendarTimeEvent + CalendarDateEvent.
  parseTicketTags reads the six tags off the raw event; tickets_
  currency is the discriminator so non-AIO calendar events (which
  don't have these tags) cleanly produce undefined.
- ActivityTicketInfo grows `sold` + `allowFiat` + `fiatCurrency`
  for the buyer surfaces, drops the never-populated `total` field,
  makes `available` optional (undefined = unlimited capacity).
- Both calendar→Activity converters now populate ticketInfo via
  ticketTagsToInfo so Nostr-sourced activities carry the inventory
  info that was previously only on LNbits drafts.
- ActivityCard handles the three-state available display
  (unlimited / count / sold-out) instead of just truthy/sold-out.

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

src/modules/activities/components/ActivityCard.vue

@@ -155,13 +155,18 @@ const placeholderBg = computed(() => {
           <span class="truncate">{{ activity.location }}</span>
         </div>
 
-        <!-- Tickets available -->
+        <!-- Tickets available. `available === undefined` means
+             unlimited capacity (no `tickets_available` tag was
+             published); show the price-only line in that case. -->
         <div
           v-if="activity.ticketInfo"
           class="flex items-center gap-1.5 text-sm text-muted-foreground"
         >
           <Ticket class="w-3.5 h-3.5 shrink-0" />
-          <span v-if="activity.ticketInfo.available > 0">
+          <span v-if="activity.ticketInfo.available === undefined">
+            {{ t('activities.detail.unlimitedTickets', 'Unlimited tickets') }}
+          </span>
+          <span v-else-if="activity.ticketInfo.available > 0">
             {{ t('activities.detail.ticketsAvailable', { count: activity.ticketInfo.available }) }}
           </span>
           <span v-else class="text-destructive font-medium">

src/modules/activities/types/activity.ts

@@ -1,6 +1,6 @@
 import ngeohash from 'ngeohash'
 import type { ActivityCategory } from './category'
-import type { CalendarTimeEvent, CalendarDateEvent } from './nip52'
+import type { CalendarTimeEvent, CalendarDateEvent, TicketTags } from './nip52'
 import type { TicketedEvent } from './ticket'
 
 /**
@@ -74,8 +74,26 @@ export interface OrganizerInfo {
 export interface ActivityTicketInfo {
   price: number
   currency: string
-  available: number
-  total: number
+  /** Remaining capacity. Undefined means unlimited. */
+  available?: number
+  /** Running paid count. */
+  sold: number
+  /** Whether the organizer enabled fiat checkout. */
+  allowFiat: boolean
+  /** Fiat settle currency when allowFiat is true. */
+  fiatCurrency?: string
+}
+
+function ticketTagsToInfo(ticket: TicketTags | undefined): ActivityTicketInfo | undefined {
+  if (!ticket) return undefined
+  return {
+    price: ticket.price,
+    currency: ticket.currency,
+    available: ticket.available,
+    sold: ticket.sold,
+    allowFiat: ticket.allowFiat,
+    fiatCurrency: ticket.fiatCurrency,
+  }
 }
 
 /**
@@ -104,6 +122,7 @@ export function calendarTimeEventToActivity(event: CalendarTimeEvent, organizer?
     geohash: event.geohash,
     category,
     tags: event.hashtags,
+    ticketInfo: ticketTagsToInfo(event.ticket),
     isPrivate: false,
     createdAt: new Date(event.createdAt * 1000),
   }
@@ -140,6 +159,7 @@ export function calendarDateEventToActivity(event: CalendarDateEvent, organizer?
     geohash: event.geohash,
     category,
     tags: event.hashtags,
+    ticketInfo: ticketTagsToInfo(event.ticket),
     isPrivate: false,
     createdAt: new Date(event.createdAt * 1000),
   }

src/modules/activities/types/nip52.ts

@@ -17,6 +17,27 @@ export const NIP52_KINDS = {
 
 export type Nip52Kind = typeof NIP52_KINDS[keyof typeof NIP52_KINDS]
 
+/**
+ * AIO custom tags carried on ticketed calendar events. The aiolabs/events
+ * extension adds these so connected clients can render the buy CTA + the
+ * "X tickets remaining" badge without an extra REST hop. Absent when the
+ * event was published by a non-AIO client.
+ */
+export interface TicketTags {
+  /** Remaining capacity. Undefined means unlimited. */
+  available?: number
+  /** Running paid-count. */
+  sold: number
+  /** Price per ticket in the event's `currency`. */
+  price: number
+  /** Currency string (e.g. 'sat', 'sats', 'USD'). */
+  currency: string
+  /** Whether the organizer enabled fiat checkout. */
+  allowFiat: boolean
+  /** Fiat settle currency when allowFiat is true. */
+  fiatCurrency?: string
+}
+
 /**
  * Parsed NIP-52 date-based calendar event (kind 31922)
  */
@@ -36,6 +57,7 @@ export interface CalendarDateEvent {
   references: string[]
   id: string
   createdAt: number
+  ticket?: TicketTags
 }
 
 /**
@@ -59,6 +81,7 @@ export interface CalendarTimeEvent {
   references: string[]
   id: string
   createdAt: number
+  ticket?: TicketTags
 }
 
 export interface Participant {
@@ -96,6 +119,35 @@ function getTagValues(tags: string[][], tagName: string): string[] {
   return tags.filter(t => t[0] === tagName).map(t => t[1])
 }
 
+/**
+ * Parse the AIO ticket_* tags off a NIP-52 calendar event. Returns
+ * undefined when the event carries no ticket info (e.g. an event
+ * published by a non-AIO client or a non-ticketed AIO event — though
+ * the latter doesn't currently exist since every aiolabs/events row
+ * has a price + currency).
+ *
+ * `tickets_currency` is the discriminator: when absent, the event has
+ * no inventory metadata and the buy UI stays hidden.
+ */
+function parseTicketTags(tags: string[][]): TicketTags | undefined {
+  const currency = getTagValue(tags, 'tickets_currency')
+  if (!currency) return undefined
+
+  const availableStr = getTagValue(tags, 'tickets_available')
+  const soldStr = getTagValue(tags, 'tickets_sold')
+  const priceStr = getTagValue(tags, 'tickets_price')
+  const allowFiatStr = getTagValue(tags, 'tickets_allow_fiat')
+
+  return {
+    available: availableStr != null ? Number(availableStr) : undefined,
+    sold: soldStr != null ? Number(soldStr) : 0,
+    price: priceStr != null ? Number(priceStr) : 0,
+    currency,
+    allowFiat: allowFiatStr === 'true',
+    fiatCurrency: getTagValue(tags, 'tickets_fiat_currency'),
+  }
+}
+
 /**
  * Parse a NIP-52 start/end tag value to a unix timestamp in seconds.
  * Handles: unix seconds, unix milliseconds, and ISO date strings.
@@ -166,6 +218,7 @@ export function parseCalendarTimeEvent(event: NostrEvent): CalendarTimeEvent | n
     references: getTagValues(event.tags, 'r'),
     id: event.id,
     createdAt: event.created_at,
+    ticket: parseTicketTags(event.tags),
   }
 }
 
@@ -213,6 +266,7 @@ export function parseCalendarDateEvent(event: NostrEvent): CalendarDateEvent | n
     references: getTagValues(event.tags, 'r'),
     id: event.id,
     createdAt: event.created_at,
+    ticket: parseTicketTags(event.tags),
   }
 }