feat: Sidecar V2 — multi-pool provider proxy with 429 cooldown

- proxy.py: Fix route path duplication (v1/v1 → v1) when upstream
  base URL already includes /v1 prefix
- proxy.py: Fix _emergency_count global variable for metrics tracking
- server.py: Add logging.basicConfig(level=logging.INFO) for structlog
  INFO-level log visibility
- Full multi-pool routing: primary → fallback → emergency passthrough
- Per-backend rate limiting with RPM-based token bucket
- 429 cooldown mechanism with automatic recovery
- Dashboard with SSE real-time monitoring
- Admin API for backend/pool/config management
- SQLite-backed persistence with encrypted API key storage
- Docker compose deployment

Deployed by opengineer 严维序 as BIZ-50 Step 4

docker-compose.yml

@@ -0,0 +1,23 @@
+# Sidecar V2 — Multi-Pool Provider Proxy
+services:
+  sidecar-v2:
+    build: .
+    container_name: sidecar-v2
+    restart: unless-stopped
+    ports:
+      - "9190:9190"  # Main proxy + admin API + dashboard
+      - "9191:9191"  # Prometheus metrics
+    env_file:
+      - .env
+    environment:
+      - SIDECAR_HOST=0.0.0.0
+      - SIDECAR_PORT=9190
+      - SIDECAR_METRICS_PORT=9191
+      - SIDECAR_DB_PATH=/app/data/sidecar_v2.db
+      - SIDECAR_BACKUP_DIR=/app/data/backups
+    volumes:
+      - sidecar-data:/app/data
+
+volumes:
+  sidecar-data:
+    driver: local