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>

apps/web/src/lib/api-client.ts

@@ -1,3 +1,5 @@
+import { getFaro } from "./faro";
+
 const API_URL = "/api";
 
 type RequestOptions = {
@@ -29,11 +31,15 @@ class ApiClient {
     const data = await res.json();
 
     if (!res.ok) {
-      throw new ApiError(
+      const error = new ApiError(
         data?.error?.message || "İstek başarısız",
         data?.error?.code || "UNKNOWN",
         res.status,
       );
+      getFaro()?.api.pushError(error, {
+        context: { method, path, statusCode: String(res.status) },
+      });
+      throw error;
     }
 
     return data.data !== undefined ? data.data : data;
@@ -65,11 +71,15 @@ class ApiClient {
     const data = await res.json();
 
     if (!res.ok) {
-      throw new ApiError(
+      const error = new ApiError(
         data?.error?.message || "Yükleme başarısız",
         data?.error?.code || "UNKNOWN",
         res.status,
       );
+      getFaro()?.api.pushError(error, {
+        context: { method: "POST", path, statusCode: String(res.status) },
+      });
+      throw error;
     }
 
     return data.data !== undefined ? data.data : data;

apps/web/src/lib/faro.ts

@@ -0,0 +1,59 @@
+import type { Faro } from "@grafana/faro-web-sdk";
+
+let faro: Faro | null = null;
+
+export async function initFaro() {
+  if (import.meta.env.VITE_FARO_ENABLED !== "true") return;
+
+  const collectorUrl = import.meta.env.VITE_FARO_COLLECTOR_URL;
+  if (!collectorUrl) {
+    console.warn("[faro] VITE_FARO_COLLECTOR_URL is required when Faro is enabled");
+    return;
+  }
+
+  try {
+    const { initializeFaro, getWebInstrumentations } = await import("@grafana/faro-web-sdk");
+    const { TracingInstrumentation } = await import("@grafana/faro-web-tracing");
+
+    faro = initializeFaro({
+      url: collectorUrl,
+      app: {
+        name: "saseweb",
+        version: "2.0.0",
+        environment: import.meta.env.MODE,
+      },
+      instrumentations: [
+        ...getWebInstrumentations({ captureConsole: false }),
+        new TracingInstrumentation({
+          instrumentationOptions: {
+            propagateTraceHeaderCorsUrls: [/\/api\//],
+          },
+        }),
+      ],
+    });
+
+    console.log("[faro] Frontend observability initialized");
+  } catch (err) {
+    console.warn("[faro] Initialization failed:", (err as Error).message);
+  }
+}
+
+export function getFaro() {
+  return faro;
+}
+
+/** Start a programmatic user action (auto-completes 100ms after last linked event) */
+export function startAction(
+  name: string,
+  attributes?: Record<string, string>,
+) {
+  faro?.api.startUserAction(name, attributes);
+}
+
+/** Push a Faro event (for non-action tracking like page-level events) */
+export function pushEvent(
+  name: string,
+  attributes?: Record<string, string>,
+) {
+  faro?.api.pushEvent(name, attributes);
+}