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/scripts/generate_images.py

@@ -0,0 +1,62 @@
+#!/usr/bin/env python3
+"""Batch-generate recipe images using OpenAI DALL-E 3.
+
+Usage:
+    python scripts/generate_images.py --limit 10 --missing-only
+    python scripts/generate_images.py --recipe-id <uuid>
+"""
+from __future__ import annotations
+
+import argparse
+import os
+import sys
+from pathlib import Path
+
+# Ensure imports resolve regardless of cwd.
+_ = sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
+
+from app.database import get_db as _get_db
+from app.services.image_generation import generate_images_batch
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="Generate recipe images via DALL-E 3")
+    parser.add_argument("--limit", type=int, default=10, help="Max recipes to process")
+    parser.add_argument("--missing-only", action="store_true", default=True, help="Only recipes without images")
+    parser.add_argument("--force", action="store_true", default=False, help="Overwrite existing images")
+    parser.add_argument("--recipe-id", type=str, default=None, help="Generate for a single recipe")
+    args = parser.parse_args()
+
+    # FastAPI DB dependency is a generator; consume it.
+    # Ensure project-root .env is discoverable before importing config.
+    project_root = Path(__file__).resolve().parent.parent.parent
+    os.environ.setdefault("DATABASE_URL", os.environ.get("DATABASE_URL", ""))
+    os.environ.setdefault("AI_IMAGE_ENABLED", os.environ.get("AI_IMAGE_ENABLED", "true"))
+    os.environ.setdefault("AI_IMAGE_API_KEY", os.environ.get("AI_IMAGE_API_KEY", ""))
+    os.environ.setdefault("OPENAI_API_KEY", os.environ.get("OPENAI_API_KEY", ""))
+
+    db_gen = _get_db()
+    db = next(db_gen)
+
+    recipe_ids = [args.recipe_id] if args.recipe_id else None
+
+    result = generate_images_batch(
+        db,
+        recipe_ids=recipe_ids,
+        missing_only=args.missing_only,
+        force=args.force,
+        limit=args.limit,
+    )
+
+    print(f"Total:     {result['total']}")
+    print(f"Succeeded: {result['succeeded']}")
+    print(f"Failed:    {result['failed']}")
+    print(f"Skipped:   {result['skipped']}")
+    for rid, info in result["results"].items():
+        print(f"  {rid}: {info['status']} – {info['url'] or '—'}")
+
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())