Fix ticket adjust: commit before cart-summary fetch

The tickets adjust_quantity route fetches cart-summary from cart, which
calls back to events for ticket counts. Without committing first, the
callback misses the just-adjusted tickets.

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

events/bp/tickets/routes.py

@@ -286,6 +286,10 @@ def register() -> Blueprint:
                         ticket_type_id=tt.id,
                     )
 
+        # Commit so cart's callback to events sees the updated tickets
+        await g.tx.commit()
+        g.tx = await g.s.begin()
+
         # Compute cart count for OOB mini-cart update
         from shared.infrastructure.data_client import fetch_data
         from shared.contracts.dtos import CartSummaryDTO, dto_from_dict