Initial commit: clean project structure

- Backend: FastAPI + SQLAlchemy + Celery (Python 3.11+)
- Frontend: Vue 3 + TypeScript + Pinia + Tailwind
- Admin Frontend: separate Vue 3 app for management
- Docker Compose: 9 services orchestration
- Specs: design prototypes, memory system PRD, product roadmap

Cleanup performed:
- Removed temporary debug scripts from backend root
- Removed deprecated admin_app.py (embedded UI)
- Removed duplicate docs from admin-frontend
- Updated .gitignore for Vite cache and egg-info

backend/app/services/provider_cache.py

@@ -0,0 +1,31 @@
+"""In-memory cache for providers loaded from DB."""
+
+from collections import defaultdict
+from typing import Literal
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.db.admin_models import Provider
+
+ProviderType = Literal["text", "image", "tts", "storybook"]
+
+_cache: dict[ProviderType, list[Provider]] = defaultdict(list)
+
+
+async def reload_providers(db: AsyncSession):
+    result = await db.execute(select(Provider).where(Provider.enabled == True))  # noqa: E712
+    providers = result.scalars().all()
+    grouped: dict[ProviderType, list[Provider]] = defaultdict(list)
+    for p in providers:
+        grouped[p.type].append(p)
+    # sort by priority desc, then weight desc
+    for k in grouped:
+        grouped[k].sort(key=lambda x: (x.priority, x.weight), reverse=True)
+    _cache.clear()
+    _cache.update(grouped)
+    return _cache
+
+
+def get_providers(provider_type: ProviderType) -> list[Provider]:
+    return _cache.get(provider_type, [])