Add ticket-to-cart integration

Reserved tickets now flow through the cart and checkout pipeline:
- TicketDTO gains price, entry_id, order_id, calendar_container_id
- CartSummaryDTO gains ticket_count, ticket_total
- 6 new CalendarService methods for ticket lifecycle
- cart_summary includes tickets; login adoption migrates tickets
- New _ticket_items.html template for checkout return page

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

contracts/dtos.py

@@ -55,6 +55,10 @@ class TicketDTO:
     calendar_name: str | None = None
     created_at: datetime | None = None
     checked_in_at: datetime | None = None
+    entry_id: int | None = None
+    price: Decimal | None = None
+    order_id: int | None = None
+    calendar_container_id: int | None = None
 
 
 @dataclass(frozen=True, slots=True)
@@ -127,3 +131,5 @@ class CartSummaryDTO:
     calendar_count: int = 0
     calendar_total: Decimal = Decimal("0")
     items: list[CartItemDTO] = field(default_factory=list)
+    ticket_count: int = 0
+    ticket_total: Decimal = Decimal("0")

contracts/protocols.py

@@ -82,6 +82,31 @@ class CalendarService(Protocol):
         self, session: AsyncSession, post_ids: list[int],
     ) -> dict[int, list[CalendarEntryDTO]]: ...
 
+    async def pending_tickets(
+        self, session: AsyncSession, *, user_id: int | None, session_id: str | None,
+    ) -> list[TicketDTO]: ...
+
+    async def tickets_for_page(
+        self, session: AsyncSession, page_id: int, *, user_id: int | None, session_id: str | None,
+    ) -> list[TicketDTO]: ...
+
+    async def claim_tickets_for_order(
+        self, session: AsyncSession, order_id: int, user_id: int | None,
+        session_id: str | None, page_post_id: int | None,
+    ) -> None: ...
+
+    async def confirm_tickets_for_order(
+        self, session: AsyncSession, order_id: int,
+    ) -> None: ...
+
+    async def get_tickets_for_order(
+        self, session: AsyncSession, order_id: int,
+    ) -> list[TicketDTO]: ...
+
+    async def adopt_tickets_for_user(
+        self, session: AsyncSession, user_id: int, session_id: str,
+    ) -> None: ...
+
 
 @runtime_checkable
 class MarketService(Protocol):