fix(l1): make get_ticket keyword-only for consistency

T11 review caught that get_ticket was the one function without the *, marker
all other functions in the module use. One-line fix, no caller impact.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/app/services/internal_ticket_service.py

@@ -54,7 +54,7 @@ async def update_status(
     return ticket
 
 
-async def get_ticket(db: AsyncSession, ticket_id: UUID) -> Optional[InternalTicket]:
+async def get_ticket(db: AsyncSession, *, ticket_id: UUID) -> Optional[InternalTicket]:
     """Fetch a ticket by ID. Returns None if not found."""
     return await db.get(InternalTicket, ticket_id)