fix(sidecar-v2): incorporate review feedback - P0/P1 fixes

P0 fixes:
- Admin API Bearer Token auth middleware
- Encryption key missing -> CRITICAL log + sys.exit(1)
- Prometheus metrics endpoint (:9191)
- requirements.txt + Dockerfile + docker-compose.yml + systemd + nginx

P1 fixes:
- Dead code removed from _refresh_cooldowns()
- Stream detection fixed (text/event-stream only)
- Emergency passthrough (10% RPM retry before 503)
- Active health probing for backends
- SQLite daily backup loop with retention
- Chart.js CDN fallback
- Key rotation SOP document
- JSON log format support
- Deploy files: systemd unit + nginx config

BIZ-52 review re-entry

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

services/nvidia_sidecar/docker-compose.yml

@@ -0,0 +1,26 @@
+# Sidecar V2 — Multi-Pool Provider Proxy
+version: "3.9"
+
+services:
+  sidecar-v2:
+    build: .
+    container_name: sidecar-v2
+    restart: unless-stopped
+    ports:
+      - "9190:9190"  # Main proxy + admin API + dashboard
+      - "9191:9191"  # Prometheus metrics
+    environment:
+      - SIDECAR_ENCRYPTION_KEY=${SIDECAR_ENCRYPTION_KEY}
+      - SIDECAR_ADMIN_TOKEN=${SIDECAR_ADMIN_TOKEN:-change-me}
+      - LOG_FORMAT=${LOG_FORMAT:-json}
+      - 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