feat: multi-ticket purchase (quantity 1-10 on a single invoice)

CreateTicket gains a bounded `quantity` field (Field(default=1,
ge=1, le=10)). One ticket row represents N seats on a single
invoice — no schema migration needed; the row's TicketExtra
carries the multiplier.

- api_ticket_create scales the invoice amount by quantity (after
  promo discount applies) and persists `quantity` in
  TicketExtra.quantity.
- Capacity check pre-validates that the requested quantity fits in
  the remaining seats; returns 400 with the actual remaining count
  rather than 410 sold-out so the client can surface a useful
  message.
- set_ticket_paid reads ticket.extra.quantity and adjusts
  event.sold / event.amount_tickets by that amount. Pre-existing
  rows that don't carry quantity default to 1 (TicketExtra schema
  default).
- The per-event asyncio lock added earlier covers this correctly:
  two parallel multi-ticket purchases on the same event serialize
  on counter mutation + republish.

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

models.py

@@ -122,6 +122,11 @@ class TicketExtra(BaseModel):
     email_notification_sent: bool = False
     nostr_notification_sent: bool = False
     refunded: bool = False
+    # Number of tickets purchased on this row's invoice (1-10).
+    # One row per purchase keeps the schema unchanged; quantity is
+    # surfaced separately so set_ticket_paid can adjust capacity by
+    # the right amount and the front-end can render "N tickets".
+    quantity: int = 1
 
 
 class CreateTicket(BaseModel):
@@ -133,6 +138,9 @@ class CreateTicket(BaseModel):
     nostr_identifier: str | None = None
     payment_method: str | None = None
     fiat_provider: str | None = None
+    # Number of tickets to buy on this single invoice. Bounded so a
+    # bad client can't run away with the organizer's capacity.
+    quantity: int = Field(default=1, ge=1, le=10)
 
     @root_validator
     def validate_identifiers(cls, values):

services.py

@@ -50,14 +50,19 @@ async def set_ticket_paid(ticket: Ticket) -> Ticket:
     if ticket.paid:
         return ticket
 
+    # One ticket row may represent N seats sold on a single invoice;
+    # event counters move by the row's quantity (default 1 for legacy
+    # purchases that pre-date the multi-ticket field).
+    quantity = max(1, ticket.extra.quantity)
+
     async with _event_paid_lock(ticket.event):
         ticket.paid = True
         await update_ticket(ticket)
 
         event = await get_event(ticket.event)
         assert event, "Couldn't get event from ticket being paid"
-        event.sold += 1
-        event.amount_tickets -= 1
+        event.sold += quantity
+        event.amount_tickets -= quantity
         await update_event(event)
 
         # Republish the NIP-52 calendar event so connected clients see

views_api.py

@@ -508,8 +508,16 @@ async def api_ticket_create(
         )
     if event.canceled:
         raise HTTPException(status_code=HTTPStatus.GONE, detail="Event is canceled.")
-    if event.amount_tickets > 0 and event.sold >= event.amount_tickets:
-        raise HTTPException(status_code=HTTPStatus.GONE, detail="Event is sold out.")
+    quantity = data.quantity
+    if event.amount_tickets > 0:
+        if event.sold >= event.amount_tickets:
+            raise HTTPException(status_code=HTTPStatus.GONE, detail="Event is sold out.")
+        remaining = event.amount_tickets - event.sold
+        if quantity > remaining:
+            raise HTTPException(
+                status_code=HTTPStatus.BAD_REQUEST,
+                detail=f"Only {remaining} ticket(s) remaining for this event.",
+            )
 
     name = data.name
     email = data.email
@@ -531,7 +539,7 @@ async def api_ticket_create(
                 status_code=HTTPStatus.BAD_REQUEST,
                 detail="Invalid Nostr identifier.",
             ) from exc
-    price = event.price_per_ticket
+    unit_price = event.price_per_ticket
     extra: dict[str, Any] = {"tag": "events", "name": name, "email": email}
 
     if promo_code:
@@ -543,7 +551,9 @@ async def api_ticket_create(
         # get the promocode
         promo = next(pc for pc in event.extra.promo_codes if pc.code == promo_code)
         extra["promo_code"] = promo.code
-        price = event.price_per_ticket * (1 - promo.discount_percent / 100)
+        unit_price = event.price_per_ticket * (1 - promo.discount_percent / 100)
+    # Scale by quantity AFTER the promo applies. One invoice, N tickets.
+    price = unit_price * quantity
 
     if payment_method == "fiat" and not event.allow_fiat:
         raise HTTPException(
@@ -613,6 +623,7 @@ async def api_ticket_create(
             "nostr_identifier": nostr_identifier,
             "ticket_base_url": str(request.base_url).rstrip("/"),
             "sats_paid": payment.sat,
+            "quantity": quantity,
         },
     )