feat(call): enhance call handling with user connection events and active call management

- Updated CallService to handle user connection and disconnection events, allowing for automatic management of active calls based on user status.
- Introduced methods to retrieve active calls for users and send pending call invites when users reconnect.
- Modified the Invite method to return the callee's online status, improving user experience during call invitations.
- Enhanced WSHandler to support connection and disconnection event handlers, ensuring accurate call state management.

internal/repository/call_repo.go

@@ -16,6 +16,7 @@ type CallRepository interface {
 	GetCallByIDWithParticipants(id string) (*model.CallSession, error)
 	UpdateCall(call *model.CallSession) error
 	GetActiveCallByConversationID(conversationID string) (*model.CallSession, error)
+	GetActiveCallsByUserID(userID string) ([]model.CallSession, error) // 获取用户参与的活跃通话
 
 	// 通话参与者操作
 	CreateCallParticipant(participant *model.CallParticipant) error
@@ -83,6 +84,25 @@ func (r *callRepository) GetActiveCallByConversationID(conversationID string) (*
 	return &call, nil
 }
 
+// GetActiveCallsByUserID 获取用户参与的所有活跃通话
+func (r *callRepository) GetActiveCallsByUserID(userID string) ([]model.CallSession, error) {
+	var calls []model.CallSession
+
+	// 子查询获取用户参与的通话ID
+	subQuery := r.db.Model(&model.CallParticipant{}).
+		Select("DISTINCT call_id").
+		Where("user_id = ?", userID)
+
+	err := r.db.Where("id IN (?) AND status IN ?", subQuery, []model.CallStatus{
+		model.CallStatusCalling,
+		model.CallStatusConnected,
+	}).Preload("Participants").Find(&calls).Error
+	if err != nil {
+		return nil, err
+	}
+	return calls, nil
+}
+
 // CreateCallParticipant 创建通话参与者
 func (r *callRepository) CreateCallParticipant(participant *model.CallParticipant) error {
 	return r.db.Create(participant).Error