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>

packages/config/src/index.ts

@@ -44,6 +44,16 @@ export const envSchema = z.object({
     .string()
     .transform((v) => v === "true")
     .default("false"),
+
+  // OpenTelemetry
+  OTEL_ENABLED: z
+    .string()
+    .transform((v) => v === "true")
+    .default("false"),
+  OTEL_EXPORTER_OTLP_ENDPOINT: z.string().optional(),
+  OTEL_EXPORTER_OTLP_HEADERS: z.string().optional(),
+  OTEL_SERVICE_NAME: z.string().default("sase-api"),
+  OTEL_TRACE_SAMPLE_RATE: z.coerce.number().min(0).max(1).default(1.0),
 });
 
 export type Env = z.infer<typeof envSchema>;