## API Integration
- Align LoginResponse type with full backend schema (id, fullname, company, role, etc.)
- Fix Login.tsx field mapping: res.data.user_id → res.data.id, res.data.name → res.data.fullname
- Add RoomMessage and RoomDetail interfaces for GET /api/v1/room/{room_id}
- Add getRoom() to fetch room detail with full chat history
- Add deleteRoom() for soft-delete via DELETE /api/v1/room/{room_id}?user_id=...
## Chat History Loading
- Add messagesLoaded flag to ChatRoom interface to track fetch state
- Add useEffect watching currentChatId to auto-load messages when a room is selected
- Covers both auto-selected room on page load and manual sidebar clicks
- Newly created rooms are marked messagesLoaded: true (no fetch needed)
## Delete Room
- deleteChat() now calls deleteRoom API before removing from local state
- If API fails (403/404), deletion is cancelled — room stays in sidebar
- deleteAllChats() calls deleteRoom in parallel via Promise.allSettled
- Deleted rooms disappear…
