feat(api): add Prometheus metrics and OpenTelemetry instrumentation for HTTP, auth, classifications, and diagnoses

apps/api/src/routes/metrics.ts

@@ -0,0 +1,10 @@
+import { Elysia } from 'elysia';
+import { getMetrics, getMetricsContentType } from '../lib/telemetry';
+
+export const metricsRoutes = new Elysia()
+  .get('/metrics', async () => {
+    const body = await getMetrics();
+    return new Response(body, {
+      headers: { 'Content-Type': getMetricsContentType() },
+    });
+  });