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/dashboard.html

@@ -5,6 +5,8 @@
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>Sidecar V2 — Provider Pool Dashboard</title>
 <script src="https://cdn.jsdelivr.net/npm/chart.js@4.4.0/dist/chart.umd.min.js"></script>
+<!-- CDN fallback: place chart.umd.min.js in static/ for offline deployments -->
+<script>if(typeof Chart==='undefined'){document.write('<script src="/static/chart.umd.min.js"><\/script>')}</script>
 <style>
   :root {
     --bg: #0f1117;