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/routes/public/mitra.chat.routes.js

@@ -0,0 +1,69 @@
+import { authenticate } from '../../plugins/auth.js'
+import { getMitraByFirebaseUid } from '../../services/mitra.service.js'
+import { acceptPairingRequest, declinePairingRequest } from '../../services/pairing.service.js'
+import { getActiveSessionsByMitra, endSession } from '../../services/session.service.js'
+import { subscribe } from '../../plugins/valkey.js'
+
+const resolveMitra = async (request, reply) => {
+  const mitra = await getMitraByFirebaseUid(request.firebaseUser.uid)
+  if (!mitra) {
+    return reply.code(404).send({
+      success: false,
+      error: { code: 'ACCOUNT_NOT_FOUND', message: 'Mitra account not found' },
+    })
+  }
+  if (!mitra.is_active) {
+    return reply.code(403).send({
+      success: false,
+      error: { code: 'ACCOUNT_INACTIVE', message: 'Account is inactive' },
+    })
+  }
+  request.mitra = mitra
+}
+
+export const mitraChatRoutes = async (app) => {
+  app.get('/incoming', { preHandler: [authenticate, resolveMitra] }, async (request, reply) => {
+    const mitraId = request.mitra.id
+
+    // SSE stream for incoming chat requests
+    reply.raw.writeHead(200, {
+      'Content-Type': 'text/event-stream',
+      'Cache-Control': 'no-cache',
+      'Connection': 'keep-alive',
+    })
+
+    // Keep-alive ping
+    const pingInterval = setInterval(() => {
+      reply.raw.write(': ping\n\n')
+    }, 15_000)
+
+    const unsubscribe = subscribe(`mitra:${mitraId}:requests`, (data) => {
+      reply.raw.write(`data: ${JSON.stringify(data)}\n\n`)
+    })
+
+    request.raw.on('close', () => {
+      clearInterval(pingInterval)
+      unsubscribe()
+    })
+  })
+
+  app.post('/:sessionId/accept', { preHandler: [authenticate, resolveMitra] }, async (request, reply) => {
+    const session = await acceptPairingRequest(request.params.sessionId, request.mitra.id)
+    return reply.send({ success: true, data: session })
+  })
+
+  app.post('/:sessionId/decline', { preHandler: [authenticate, resolveMitra] }, async (request, reply) => {
+    await declinePairingRequest(request.params.sessionId, request.mitra.id)
+    return reply.send({ success: true })
+  })
+
+  app.get('/sessions/active', { preHandler: [authenticate, resolveMitra] }, async (request, reply) => {
+    const sessions = await getActiveSessionsByMitra(request.mitra.id)
+    return reply.send({ success: true, data: sessions })
+  })
+
+  app.post('/sessions/:sessionId/end', { preHandler: [authenticate, resolveMitra] }, async (request, reply) => {
+    const session = await endSession(request.params.sessionId, 'mitra')
+    return reply.send({ success: true, data: session })
+  })
+}