feat(backend): wire exclude_recipe_ids, verify MealPlan votes schema, add image generation service

- api/meal_plans.py: /regenerate now passes exclude_recipe_ids into generate_meal_plan
- planner/generate.py: filter recipe_dicts by exclude_recipe_ids set
- image_generation.py: OpenAI gpt-image-1 client with prompt building, b64_json handling
- main.py: StaticFiles mount at /static for generated images
- admin.py: POST /api/admin/trigger-images endpoint for batch generation
- scripts/generate_images.py: CLI for batch image generation
- docker-compose.yml + nginx: volume mounts for static/images persistence
- Verify MealPlanItem.votes ↔ MealPlanVote relationship is correct; no model bug exists

backend/app/services/planner/generate.py

@@ -100,6 +100,7 @@ def generate_meal_plan(
     week_start_date: date,
     config: PlannerConfig = DEFAULT,
     today: Optional[date] = None,
+    exclude_recipe_ids: Optional[Set[UUID]] = None,
 ) -> GenerationResult:
     today = today or date.today()
     family = db.query(FamilyProfile).filter(FamilyProfile.id == family_id).first()
@@ -107,6 +108,7 @@ def generate_meal_plan(
         raise ValueError(f"family_profile {family_id} not found")
 
     recipes = db.query(Recipe).all()
+    exclude_set = exclude_recipe_ids or set()
     recipe_dicts = [
         {
             "id": r.id,
@@ -120,6 +122,7 @@ def generate_meal_plan(
             "servings": r.servings or 4,
         }
         for r in recipes
+        if r.id not in exclude_set
     ]
 
     recipe_ingredient_ids: Dict[UUID, Set[UUID]] = {}