[RAPID] feat: 메신저 기능 구현 (Socket.IO 실시간 채팅)

- DB: messenger_rooms/participants/messages/reactions/files 테이블 생성
- Backend: REST API 9개 엔드포인트 + Socket.IO 실시간 핸들러
- Frontend: Gmail 스타일 FAB + 모달, 채팅방 목록, 채팅 패널
- 기능: DM/그룹/채널, 파일 첨부, 이모지 리액션, 멘션, 스레드
- 알림: 토스트 on/off 토글, FAB 읽지 않은 배지

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

[RAPID-fix] 메신저 API snake_case→camelCase 변환 및 Socket.IO URL 수정

- useRooms/useMessages/useCompanyUsers 훅에서 DB 응답 camelCase 변환
- Socket.IO 기본 연결 URL 3001 → 8080 수정
- runMigration.ts 마이그레이션 파일 경로 수정 (../../ → ../../../)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

[RAPID-fix] 방 생성 API camelCase/snake_case 호환 처리

- createRoom 컨트롤러에서 participantIds/type/name (camelCase) fallback 추가

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

[RAPID-fix] 메시지 전송 API 추가 (sendMessage 라우트/컨트롤러 누락)

- POST /api/messenger/rooms/:roomId/messages 라우트 등록
- MessengerController.sendMessage 메서드 추가

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend-node/src/routes/messengerRoutes.ts

@@ -0,0 +1,45 @@
+import { Router } from 'express';
+import { messengerController } from '../controllers/messengerController';
+import { authenticateToken } from '../middleware/authMiddleware';
+import { uploadMessengerFile } from '../config/multerMessengerConfig';
+
+const router = Router();
+
+// All messenger routes require authentication
+router.use(authenticateToken);
+
+// GET /api/messenger/rooms - Get my rooms
+router.get('/rooms', (req, res) => messengerController.getRooms(req, res));
+
+// POST /api/messenger/rooms - Create a room
+router.post('/rooms', (req, res) => messengerController.createRoom(req, res));
+
+// GET /api/messenger/rooms/:roomId/messages - Get messages
+router.get('/rooms/:roomId/messages', (req, res) => messengerController.getMessages(req, res));
+
+// POST /api/messenger/rooms/:roomId/messages - Send message
+router.post('/rooms/:roomId/messages', (req, res) => messengerController.sendMessage(req, res));
+
+// POST /api/messenger/rooms/:roomId/read - Mark as read
+router.post('/rooms/:roomId/read', (req, res) => messengerController.markAsRead(req, res));
+
+// PUT /api/messenger/rooms/:roomId - Update room
+router.put('/rooms/:roomId', (req, res) => messengerController.updateRoom(req, res));
+
+// POST /api/messenger/files/upload - Upload files
+router.post(
+  '/files/upload',
+  uploadMessengerFile.array('files', 10),
+  (req, res) => messengerController.uploadFile(req, res)
+);
+
+// GET /api/messenger/files/:fileId - Download file
+router.get('/files/:fileId', (req, res) => messengerController.downloadFile(req, res));
+
+// GET /api/messenger/users - Get company users
+router.get('/users', (req, res) => messengerController.getCompanyUsers(req, res));
+
+// GET /api/messenger/unread - Get unread count
+router.get('/unread', (req, res) => messengerController.getUnreadCount(req, res));
+
+export default router;