Phase 3.1 WS2: Backend FCM fallback, ping config, unread API

- Add require_mitra_ping + mitra_ping_interval_seconds config keys (migration)
- Add getMitraPingConfig/setMitraPingConfig to config service
- Add GET/PATCH /internal/config/mitra-ping routes for control center
- Update mitra status service: honor ping config in auto-offline sweep,
  include ping config in GET /api/mitra/status response
- Enhance pairing FCM payload with action: 'open_accept' for deep-link
- Add FCM fallback to closure.service (initiateEarlyEnd, completeSession)
- Add FCM fallback to session-timer.service (onSessionExpired)
- Add unread count queries (getActiveSessionByCustomerWithUnread,
  getActiveSessionsByMitraWithUnread)
- Add GET /api/client/chat/session/active-with-unread route
- Add GET /api/mitra/chat-requests/sessions/active-with-unread route

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

backend/src/services/closure.service.js

@@ -2,6 +2,7 @@ import { getDb } from '../db/client.js'
 import { publish } from '../plugins/valkey.js'
 import { clearSessionTimer, clearClosureGraceTimer } from './session-timer.service.js'
 import { sendToSessionParticipant } from '../plugins/websocket.js'
+import { sendPushNotification } from './notification.service.js'
 import { UserType, SessionStatus, EndedBy, WsMessage } from '../constants.js'
 
 const sql = getDb()
@@ -53,10 +54,25 @@ export const completeSession = async (sessionId) => {
   `
   if (!session) return null
 
-  // Notify both parties
+  // Notify both parties, FCM fallback if WebSocket is down
   const data = { type: WsMessage.SESSION_COMPLETED, session_id: sessionId }
-  sendToSessionParticipant(sessionId, UserType.CUSTOMER, data)
-  sendToSessionParticipant(sessionId, UserType.MITRA, data)
+  const customerSent = sendToSessionParticipant(sessionId, UserType.CUSTOMER, data)
+  const mitraSent = sendToSessionParticipant(sessionId, UserType.MITRA, data)
+
+  if (!customerSent) {
+    await sendPushNotification(UserType.CUSTOMER, session.customer_id, {
+      title: 'Sesi Selesai',
+      body: 'Sesi curhat kamu telah selesai.',
+      data: { type: WsMessage.SESSION_COMPLETED, session_id: sessionId },
+    })
+  }
+  if (!mitraSent) {
+    await sendPushNotification(UserType.MITRA, session.mitra_id, {
+      title: 'Sesi Selesai',
+      body: 'Sesi curhat telah selesai.',
+      data: { type: WsMessage.SESSION_COMPLETED, session_id: sessionId },
+    })
+  }
 
   await publish(`session:${sessionId}:status`, { type: WsMessage.SESSION_ENDED, session_id: sessionId })
 
@@ -90,10 +106,25 @@ export const initiateEarlyEnd = async (sessionId, userType) => {
 
   clearSessionTimer(sessionId)
 
-  // Notify both parties to enter closure flow
+  // Notify both parties to enter closure flow, FCM fallback if WebSocket is down
   const data = { type: WsMessage.SESSION_CLOSING, session_id: sessionId, ended_by: userType }
-  sendToSessionParticipant(sessionId, UserType.CUSTOMER, data)
-  sendToSessionParticipant(sessionId, UserType.MITRA, data)
+  const customerSent = sendToSessionParticipant(sessionId, UserType.CUSTOMER, data)
+  const mitraSent = sendToSessionParticipant(sessionId, UserType.MITRA, data)
+
+  if (!customerSent) {
+    await sendPushNotification(UserType.CUSTOMER, session.customer_id, {
+      title: 'Sesi Berakhir',
+      body: 'Sesi curhat kamu telah berakhir. Ketuk untuk menulis pesan penutup.',
+      data: { type: WsMessage.SESSION_CLOSING, session_id: sessionId },
+    })
+  }
+  if (!mitraSent) {
+    await sendPushNotification(UserType.MITRA, session.mitra_id, {
+      title: 'Sesi Berakhir',
+      body: 'Sesi curhat telah berakhir. Ketuk untuk menulis pesan penutup.',
+      data: { type: WsMessage.SESSION_CLOSING, session_id: sessionId },
+    })
+  }
 
   return session
 }