feat: 21 meals per week (3/day) + approve/deny + generate single meal

Backend:
- Planner config: set_size=21 (was 3), top_k=30 (was 20)
- generate.py: distribute 21 recipes across 7 days × 3 meal types
- meals.py: add POST /items/{id}/approve, /items/{id}/deny
- meals.py: add POST /{plan_id}/generate-item for empty slots

Frontend:
- Dashboard: Approve/Deny buttons on pending meal cards
- Dashboard: Generate button in empty meal slots
- API client: approveItem, denyItem, generateItem methods

Build: TypeScript compiles clean, Python syntax verified.

backend/app/services/planner/generate.py

@@ -177,11 +177,14 @@ def generate_meal_plan(
     db.flush()
 
     for index, scored_recipe in enumerate(chosen):
+        day = (index % 7) + 1           # 1..7 (Mon..Sun)
+        meal_type_index = index // 7    # 0=breakfast, 1=lunch, 2=dinner
+        meal_type = [MealType.BREAKFAST, MealType.LUNCH, MealType.DINNER][meal_type_index]
         item = MealPlanItem(
             meal_plan_id=plan.id,
             recipe_id=scored_recipe.recipe_id,
-            day_of_week=index + 1,         # Mon=1, Tue=2, Wed=3 by default
-            meal_type=MealType.DINNER,
+            day_of_week=day,
+            meal_type=meal_type,
             approval_status=MealPlanItemStatus.pending,
             estimated_cost=scored_recipe.cost.total_cost,
         )