feat(sidecar-v2): implement multi-pool provider proxy with cooldown, rate limiting, WebUI

BIZ-52 Step3 开发实现:
- storage: backend/usage/cooldown/config CRUD with SQLite WAL
- crypto: AES-256-GCM API key encryption
- pool_manager: primary/fallback pool routing
- cooldown_manager: 429 exponential backoff cooldown
- rate_limiter: per-backend token bucket RPM control
- router: model → backend routing with pool priority
- proxy: multi-pool request forwarding with retry
- server: FastAPI admin API + OpenAI-compatible proxy + SSE
- dashboard: WebUI with provider CRUD, stats, charts

Co-authored-by: multica-agent <github@multica.ai>

services/nvidia_sidecar/main.py

@@ -0,0 +1,17 @@
+"""Sidecar V2 entry point."""
+
+import uvicorn
+from config import config
+
+
+def main():
+    uvicorn.run(
+        "server:app",
+        host=config.host,
+        port=config.port,
+        log_level=config.log_level.lower(),
+    )
+
+
+if __name__ == "__main__":
+    main()