Fix adventures list 500 on Postgres (GROUP BY)

list_adventures selected Scenario.title while grouping only by
Adventure.id. SQLite tolerates selecting an ungrouped column, so it
worked locally, but Postgres (Neon) rejects it — the adventures list
endpoint 500'd on the live deploy, so saved adventures could not be
listed or resumed. Add Scenario.title to the GROUP BY.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TEpWMjnfPqzZ13nPMoGhs5

backend/app/routers/adventures.py

@@ -35,7 +35,11 @@ def list_adventures(db: Session = Depends(get_db), user: models.User = CurrentUs
         .outerjoin(models.Action)
         .outerjoin(models.Scenario, models.Adventure.scenario_id == models.Scenario.id)
         .filter(models.Adventure.user_id == user.id)
-        .group_by(models.Adventure.id)
+        # Group by both PKs: Postgres requires every selected column to be
+        # grouped or aggregated. Adventure.* rides on its own grouped PK, but
+        # Scenario.title comes from a joined table and must be listed too
+        # (SQLite is lax here; Postgres rejects it).
+        .group_by(models.Adventure.id, models.Scenario.title)
         .order_by(models.Adventure.updated_at.desc())
         .all()
     )