feat(call): add media type support to call invite functionality

- Updated the WSHandler to include a media type field in the call invite request, allowing differentiation between voice and video calls.
- Modified the CallService interface and implementation to accept the media type parameter during call invitations, enhancing call handling capabilities.

internal/handler/ws_handler.go

@@ -450,6 +450,7 @@ func (h *WSHandler) handleCallInvite(ctx context.Context, client *ws.Client, pay
 	var req struct {
 		CalleeID       string `json:"callee_id"`
 		ConversationID string `json:"conversation_id"`
+		MediaType      string `json:"call_type"` // voice 或 video
 	}
 	if err := json.Unmarshal(payload, &req); err != nil {
 		h.wsHub.SendError(client, "parse_error", "invalid call_invite format")
@@ -460,7 +461,13 @@ func (h *WSHandler) handleCallInvite(ctx context.Context, client *ws.Client, pay
 		return
 	}
 
-	call, err := h.callService.Invite(ctx, client.UserID, req.CalleeID, req.ConversationID)
+	// 前端传的 call_type 是 voice/video，默认为 voice
+	mediaType := req.MediaType
+	if mediaType != "video" {
+		mediaType = "voice"
+	}
+
+	call, err := h.callService.Invite(ctx, client.UserID, req.CalleeID, req.ConversationID, mediaType)
 	if err != nil {
 		zap.L().Warn("Failed to invite call",
 			zap.String("caller_id", client.UserID),