feat(call): implement group calling and enhance call management

Introduces group calling capabilities, including group invites and participant
lifecycle management. Enhances the existing call system with support for
media types (voice/video) and improved participant tracking.

- Add `GroupInvite` and `ParticipantJoin/Leave` to `CallService`.
- Implement WebSocket handlers for `call_group_invite` and
  `call_participant_join`.
- Update `CallSession` model to support group IDs, media types, and
  tracking who ended the call.
- Integrate `GroupService` into `CallService` via dependency injection.
- Add error constants for group call limitations and participant capacity.
- Update LiveKit webhook handling to process participant leave events.

Refactor grade synchronization to remove semester-based filtering in favor
of a more flexible user-based approach and improve GPA summary updates.

internal/wire/service.go

@@ -460,8 +460,9 @@ func ProvideCallService(
 	cfg *config.Config,
 	db *gorm.DB,
 	redisClient *redis.Client,
+	groupService service.GroupService,
 ) service.CallService {
-	return service.NewCallService(callRepo, publisher, cfg, db, redisClient)
+	return service.NewCallService(callRepo, publisher, cfg, db, redisClient, groupService)
 }
 
 // ProvideLiveKitService 提供 LiveKit 服务