Fix timer action 500s after FastAPI upgrade

FastAPI 0.141 raises when response serialization hits a lazy-load
(current_block.subject.options) in async context, where 0.115 silently
skipped it. Eager-load Subject.options in session get/timer and the TV
dashboard queries. Pin pydantic 2.13.5.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

backend/app/routers/dashboard.py

@@ -39,7 +39,7 @@ async def get_dashboard(tv_token: int, db: AsyncSession = Depends(get_db)):
             DailySession.session_date == date.today(),
             DailySession.is_active == True,
         )
-        .options(selectinload(DailySession.current_block))
+        .options(selectinload(DailySession.current_block).selectinload(ScheduleBlock.subject).selectinload(Subject.options))
         .limit(1)
     )
     session = session_result.scalar_one_or_none()

backend/app/routers/sessions.py

@@ -172,7 +172,7 @@ async def get_session(
         select(DailySession)
         .join(Child)
         .where(DailySession.id == session_id, Child.user_id == current_user.id)
-        .options(selectinload(DailySession.current_block).selectinload(ScheduleBlock.subject))
+        .options(selectinload(DailySession.current_block).selectinload(ScheduleBlock.subject).selectinload(Subject.options))
     )
     session = result.scalar_one_or_none()
     if not session:
@@ -191,7 +191,7 @@ async def timer_action(
         select(DailySession)
         .join(Child)
         .where(DailySession.id == session_id, Child.user_id == current_user.id)
-        .options(selectinload(DailySession.current_block).selectinload(ScheduleBlock.subject))
+        .options(selectinload(DailySession.current_block).selectinload(ScheduleBlock.subject).selectinload(Subject.options))
     )
     session = result.scalar_one_or_none()
     if not session:

backend/requirements.txt

@@ -9,6 +9,7 @@ PyJWT==2.15.0
 cryptography==50.0.1
 passlib[bcrypt]==1.7.4
 bcrypt==3.2.2
+pydantic==2.13.5
 pydantic-settings==2.5.2
 alembic==1.20.0
 Mako==1.4.3