Add user ping system and room deletion functionality

Backend changes:
- Fix track deletion foreign key constraint (tracks.py)
  * Clear current_track_id from rooms before deleting track
  * Prevent deletion errors when track is currently playing

- Implement user ping/keepalive system (sync.py, websocket.py, ping_task.py, main.py)
  * Track last pong timestamp for each user
  * Background task sends ping every 30s, disconnects users after 60s timeout
  * Auto-pause playback when room becomes empty
  * Remove disconnected users from room_participants

- Enhance room deletion (rooms.py)
  * Broadcast room_deleted event to all connected users
  * Close all WebSocket connections before deletion
  * Cascade delete participants, queue, and messages

Frontend changes:
- Add ping/pong WebSocket handling (activeRoom.js)
  * Auto-respond to server pings
  * Handle room_deleted event with redirect to home

- Add room deletion UI (RoomView.vue, HomeView.vue, RoomCard.vue)
  * Delete button visible only to room owner
  * Confirmation dialog with warning
  * Delete button on room cards (shows on hover)
  * Redirect to home page after deletion

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/app/services/ping_task.py

@@ -0,0 +1,88 @@
+import asyncio
+import time
+from uuid import UUID
+from datetime import datetime
+from sqlalchemy import select, delete
+from app.database import async_session
+from app.models.room import Room, RoomParticipant
+from app.services.sync import manager
+
+
+async def ping_users_task():
+    """Фоновая задача для периодического пинга пользователей и отключения неактивных"""
+    while True:
+        try:
+            await asyncio.sleep(manager.ping_interval)
+
+            current_time = time.time()
+            disconnected_users = []
+
+            # Проходим по всем активным соединениям
+            for room_id, connections in list(manager.get_all_connections().items()):
+                for websocket, user_id in list(connections):
+                    # Отправляем ping
+                    try:
+                        await websocket.send_json({"type": "ping"})
+                    except Exception:
+                        # Если не смогли отправить - помечаем на отключение
+                        disconnected_users.append((websocket, room_id, user_id))
+                        continue
+
+                    # Проверяем время последнего pong
+                    last_pong_time = manager.last_pong.get((room_id, user_id))
+                    if last_pong_time is None or (current_time - last_pong_time) > manager.ping_timeout:
+                        # Пользователь не отвечает слишком долго
+                        disconnected_users.append((websocket, room_id, user_id))
+
+            # Отключаем неактивных пользователей
+            for websocket, room_id, user_id in disconnected_users:
+                await disconnect_inactive_user(websocket, room_id, user_id)
+
+        except Exception as e:
+            print(f"Error in ping_users_task: {e}")
+            await asyncio.sleep(5)  # Подождём немного при ошибке
+
+
+async def disconnect_inactive_user(websocket, room_id: UUID, user_id: UUID):
+    """Отключить неактивного пользователя"""
+    try:
+        # Закрываем WebSocket соединение
+        await websocket.close(code=1000, reason="Ping timeout")
+    except Exception:
+        pass
+
+    # Удаляем из менеджера соединений
+    manager.disconnect(websocket, room_id, user_id)
+
+    # Удаляем из БД
+    async with async_session() as db:
+        await db.execute(
+            delete(RoomParticipant).where(
+                RoomParticipant.room_id == room_id,
+                RoomParticipant.user_id == user_id
+            )
+        )
+        await db.commit()
+
+        # Проверяем, остались ли участники
+        room_user_count = manager.get_room_user_count(room_id)
+
+        # Если комната пустая - ставим трек на паузу
+        if room_user_count == 0:
+            result = await db.execute(select(Room).where(Room.id == room_id))
+            room = result.scalar_one_or_none()
+            if room and room.is_playing:
+                # Сохраняем текущую позицию
+                if room.playback_started_at:
+                    elapsed = (datetime.utcnow() - room.playback_started_at).total_seconds() * 1000
+                    room.playback_position = int((room.playback_position or 0) + elapsed)
+
+                room.is_playing = False
+                room.playback_started_at = None
+                await db.commit()
+
+    # Уведомляем остальных участников
+    await manager.broadcast_to_room(
+        room_id,
+        {"type": "user_left", "user_id": str(user_id), "reason": "timeout"},
+    )