- Added RemoveMember method to RoomService and RoomServiceInterface
- Corrected RemoveMember in RoomRepository to use uuid.UUID
- Added AddParticipant and RemoveParticipant handlers
- Added POST /conversations/:id/participants route
- Added DELETE /conversations/:id/participants/:userId route
- Handlers use standard API response format
- Handlers reuse AddMember/RemoveMember service methods
Phase: PHASE-2
Priority: P1
Progress: 20/267 (7.5%)
