Phase 2 scaffold: mitra online status & pairing logic

Add mitra online/offline status with heartbeat-based auto-offline,
customer-mitra pairing via Valkey pub/sub blast, session management,
and control center dashboard with real-time stats.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/src/server.js

@@ -1,6 +1,7 @@
 import 'dotenv/config'
 import { buildPublicApp } from './app.public.js'
 import { buildInternalApp } from './app.internal.js'
+import { autoOfflineStaleMitras } from './services/mitra-status.service.js'
 
 const PUBLIC_PORT = process.env.PUBLIC_PORT || 3000
 const INTERNAL_PORT = process.env.INTERNAL_PORT || 3001
@@ -15,6 +16,16 @@ const start = async () => {
 
   await internalApp.listen({ port: INTERNAL_PORT, host: INTERNAL_HOST })
   console.log(`Internal API listening on ${INTERNAL_HOST}:${INTERNAL_PORT}`)
+
+  // Auto-offline mitras with stale heartbeat (every 30s)
+  setInterval(async () => {
+    try {
+      const count = await autoOfflineStaleMitras(45)
+      if (count > 0) console.log(`Auto-offlined ${count} stale mitra(s)`)
+    } catch (err) {
+      console.error('Auto-offline check failed:', err)
+    }
+  }, 30_000)
 }
 
 start().catch((err) => {