Add ticket +/- quantity support to shared contracts and services

- Add ticket_type_id field to TicketDTO for grouping
- Add adjust_ticket_quantity to CalendarService protocol + SQL impl
- Add stub for adjust_ticket_quantity

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

contracts/dtos.py

@@ -56,6 +56,7 @@ class TicketDTO:
     created_at: datetime | None = None
     checked_in_at: datetime | None = None
     entry_id: int | None = None
+    ticket_type_id: int | None = None
     price: Decimal | None = None
     order_id: int | None = None
     calendar_container_id: int | None = None

contracts/protocols.py

@@ -112,6 +112,12 @@ class CalendarService(Protocol):
         self, session: AsyncSession, user_id: int, session_id: str,
     ) -> None: ...
 
+    async def adjust_ticket_quantity(
+        self, session: AsyncSession, entry_id: int, count: int, *,
+        user_id: int | None, session_id: str | None,
+        ticket_type_id: int | None = None,
+    ) -> int: ...
+
     async def entry_ids_for_content(
         self, session: AsyncSession, content_type: str, content_id: int,
     ) -> set[int]: ...