feat(backend): persist plan scores on MealPlanItem

- Migration 0012 adds score (float) and components (jsonb) to meal_plan_item
- generate.py: populates score and components at create time
- schemas/MealPlanItemResponse: include score + components fields
- GET /api/meal-plans/{id}: returns persisted values instead of zeros

backend/app/services/planner/generate.py

@@ -196,6 +196,8 @@ def generate_meal_plan(
             meal_type=meal_type,
             approval_status=MealPlanItemStatus.pending,
             estimated_cost=scored_recipe.cost.total_cost,
+            score=scored_recipe.score,
+            components=scored_recipe.components,
         )
         db.add(item)