feat: Phase 8 Feedback UI + API endpoints

- New backend/app/api/feedback.py: GET/POST for meal_plan_item feedback
- MealDetail.tsx: star rating, never-suggest checkbox, reason dropdown,
  free-text comments, displays saved feedback
- frontend/src/api/index.ts + types: feedback API + TypeScript interface
- backend/app/schemas/__init__.py: model_validator maps qty→quantity for
  RecipeIngredient (fixes Pydantic validation on recipe JSONB)
- docs/HANDOFF.md: mark Phase 8 complete, update file map and date

backend/app/main.py

@@ -34,6 +34,7 @@ from app.api import ingredients as ingredients_api
 from app.api import recipes as recipes_api
 from app.api import never_suggest as never_suggest_api
 from app.api import meal_plans as meal_plans_api
+from app.api import feedback as feedback_api
 
 app.include_router(auth.router, prefix="/api/auth", tags=["auth"])
 app.include_router(profile.router, prefix="/api/profile", tags=["profile"])
@@ -50,3 +51,4 @@ app.include_router(never_suggest_api.public_router)
 app.include_router(never_suggest_api.admin_router)
 app.include_router(meal_plans_api.admin_router)
 app.include_router(meal_plans_api.public_router)
+app.include_router(feedback_api.router, prefix="/api/feedback", tags=["feedback"])