Fix: 로딩 중 강제 종료 시 stale waiting room 자동 정리

로딩 화면에서 강제 종료하면 BossRoom이 waiting 상태로 남아
재입장이 영구 차단되는 문제 수정.

- waiting 상태 2분 초과 BossRoom 자동 정리 (15초 주기)
- RequestEntry 시 해당 유저의 stale waiting room 선제 정리
- 연결된 RoomSlot도 idle로 리셋

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

internal/bossraid/repository.go

@@ -64,6 +64,18 @@ func (r *Repository) CountActiveByUsername(username string) (int64, error) {
 	return count, err
 }
 
+// FindStaleWaitingRoomsByUsername returns waiting rooms containing the given username
+// that were created before the threshold.
+func (r *Repository) FindStaleWaitingRoomsByUsername(username string, threshold time.Time) ([]BossRoom, error) {
+	escaped := strings.NewReplacer("%", "\\%", "_", "\\_").Replace(username)
+	search := `"` + escaped + `"`
+	var rooms []BossRoom
+	err := r.db.Where("status = ? AND players LIKE ? AND created_at < ?",
+		StatusWaiting, "%"+search+"%", threshold).
+		Find(&rooms).Error
+	return rooms, err
+}
+
 // --- DedicatedServer & RoomSlot ---
 
 // UpsertDedicatedServer creates or updates a server group by name.
@@ -213,6 +225,40 @@ func (r *Repository) DeleteRoomBySessionName(sessionName string) error {
 	return r.db.Unscoped().Where("session_name = ?", sessionName).Delete(&BossRoom{}).Error
 }
 
+// CleanupStaleWaitingRooms deletes BossRoom records stuck in "waiting" status
+// past the given threshold and resets their associated RoomSlots to idle.
+// This handles cases where players disconnect during loading before the Fusion session starts.
+func (r *Repository) CleanupStaleWaitingRooms(threshold time.Time) (int64, error) {
+	// 1. waiting 상태에서 threshold보다 오래된 방 조회
+	var staleRooms []BossRoom
+	if err := r.db.Where("status = ? AND created_at < ?", StatusWaiting, threshold).
+		Find(&staleRooms).Error; err != nil {
+		return 0, err
+	}
+	if len(staleRooms) == 0 {
+		return 0, nil
+	}
+
+	// 2. 연결된 슬롯을 idle로 리셋
+	staleSessionNames := make([]string, len(staleRooms))
+	for i, room := range staleRooms {
+		staleSessionNames[i] = room.SessionName
+	}
+	r.db.Model(&RoomSlot{}).
+		Where("session_name IN ? AND status = ?", staleSessionNames, SlotWaiting).
+		Updates(map[string]interface{}{
+			"status":       SlotIdle,
+			"boss_room_id": nil,
+		})
+
+	// 3. BossRoom 레코드 하드 삭제
+	result := r.db.Unscoped().
+		Where("status = ? AND created_at < ?", StatusWaiting, threshold).
+		Delete(&BossRoom{})
+
+	return result.RowsAffected, result.Error
+}
+
 // ResetStaleSlots clears instanceID for slots with stale heartbeats
 // and resets any active raids on those slots.
 func (r *Repository) ResetStaleSlots(threshold time.Time) (int64, error) {