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/client.chat.routes.js

@@ -0,0 +1,75 @@
+import { authenticate } from '../../plugins/auth.js'
+import { getCustomerByFirebaseUid } from '../../services/customer.service.js'
+import { createPairingRequest, cancelPairingRequest, getSessionStatus } from '../../services/pairing.service.js'
+import { getActiveSessionByCustomer, endSession } from '../../services/session.service.js'
+import { subscribe } from '../../plugins/valkey.js'
+
+const resolveCustomer = async (request, reply) => {
+  const customer = await getCustomerByFirebaseUid(request.firebaseUser.uid)
+  if (!customer) {
+    return reply.code(404).send({
+      success: false,
+      error: { code: 'ACCOUNT_NOT_FOUND', message: 'Customer account not found' },
+    })
+  }
+  request.customer = customer
+}
+
+export const clientChatRoutes = async (app) => {
+  app.post('/request', { preHandler: [authenticate, resolveCustomer] }, async (request, reply) => {
+    const session = await createPairingRequest(request.customer.id)
+    return reply.code(201).send({ success: true, data: session })
+  })
+
+  app.get('/request/:sessionId/status', { preHandler: [authenticate, resolveCustomer] }, async (request, reply) => {
+    const { sessionId } = request.params
+
+    // SSE stream for real-time status updates
+    reply.raw.writeHead(200, {
+      'Content-Type': 'text/event-stream',
+      'Cache-Control': 'no-cache',
+      'Connection': 'keep-alive',
+    })
+
+    // Send current status immediately
+    const current = await getSessionStatus(sessionId)
+    if (current) {
+      reply.raw.write(`data: ${JSON.stringify(current)}\n\n`)
+    }
+
+    // If already in a terminal state, close
+    if (current && ['active', 'completed', 'cancelled', 'expired'].includes(current.status)) {
+      reply.raw.end()
+      return
+    }
+
+    // Subscribe to status updates
+    const unsubscribe = subscribe(`session:${sessionId}:status`, (data) => {
+      reply.raw.write(`data: ${JSON.stringify(data)}\n\n`)
+      if (['paired', 'expired', 'session_ended'].includes(data.type)) {
+        reply.raw.end()
+        unsubscribe()
+      }
+    })
+
+    // Clean up on client disconnect
+    request.raw.on('close', () => {
+      unsubscribe()
+    })
+  })
+
+  app.post('/request/:sessionId/cancel', { preHandler: [authenticate, resolveCustomer] }, async (request, reply) => {
+    const session = await cancelPairingRequest(request.params.sessionId, request.customer.id)
+    return reply.send({ success: true, data: session })
+  })
+
+  app.get('/session/active', { preHandler: [authenticate, resolveCustomer] }, async (request, reply) => {
+    const session = await getActiveSessionByCustomer(request.customer.id)
+    return reply.send({ success: true, data: session ?? null })
+  })
+
+  app.post('/session/:sessionId/end', { preHandler: [authenticate, resolveCustomer] }, async (request, reply) => {
+    const session = await endSession(request.params.sessionId, 'customer')
+    return reply.send({ success: true, data: session })
+  })
+}