feat(call): integrate LiveKit for voice and video calling

Replace the manual WebRTC signaling implementation with LiveKit SFU. This includes:
- Adding LiveKit service, handler, and configuration.
- Updating Docker Compose to include LiveKit server, Redis, and PostgreSQL.
- Refactoring `CallService` and `WSHandler` to support LiveKit room readiness instead of raw SDP/ICE relaying.
- Adding new API endpoints for LiveKit token generation and webhooks.
- Removing deprecated WebRTC configuration and manual signaling DTOs.

internal/pkg/ws/hub.go

@@ -343,7 +343,7 @@ func (h *Hub) PublishToUserOnline(userID string, eventType string, payload any)
 }
 
 // PublishToUserOnlineReliable 可靠地发送事件给在线用户（阻塞发送）
-// 用于重要的信令消息（如 SDP, ICE candidate），确保消息送达
+// 用于重要的信令消息（如通话邀请、接听），确保消息送达
 // 如果用户不在线，返回 false
 func (h *Hub) PublishToUserOnlineReliable(userID string, eventType string, payload any) bool {
 	h.mu.RLock()