feat: add OpenTelemetry observability, Faro frontend monitoring, remove legacy Next.js app

- Add OpenTelemetry SDK with tracing, metrics, and OTLP export for API and worker
- Integrate Grafana Faro for frontend real-user monitoring
- Instrument health checks, database, Bull queues, and HTTP exception filter
- Add Grafana dashboard JSON for service overview
- Remove deprecated apps/web-nj (Next.js) — fully replaced by Vite+React frontend
- Update nginx config with OTEL collector proxy
- Minor UI fixes in schema viewer, category components, and subscription flow

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker/nginx/sites/sase.tr.conf

@@ -27,6 +27,16 @@ server {
     root /home/s/ss/apps/web/dist;
     index index.html;
 
+    # Faro telemetry proxy → Grafana Cloud (avoids CORS)
+    location /collect/ {
+        proxy_pass https://faro-collector-prod-eu-west-2.grafana.net/collect/;
+        proxy_http_version 1.1;
+        proxy_set_header Host faro-collector-prod-eu-west-2.grafana.net;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_ssl_server_name on;
+    }
+
     # Proxy API requests to NestJS backend
     location /api/ {
         proxy_pass http://127.0.0.1:4000;