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>

ecosystem.config.js

@@ -9,6 +9,8 @@ module.exports = {
       env: {
         NODE_ENV: "development",
         PORT: 4000,
+        OTEL_ENABLED: "true",
+        OTEL_SERVICE_NAME: "sase-api",
       },
       max_memory_restart: "512M",
       error_file: "../../logs/api-error.log",
@@ -40,6 +42,8 @@ module.exports = {
       exec_mode: "fork",
       env: {
         NODE_ENV: "production",
+        OTEL_ENABLED: "true",
+        OTEL_SERVICE_NAME: "sase-worker",
       },
       max_memory_restart: "256M",
       error_file: "../../logs/worker-error.log",