fix: prevent empty name/description from overwriting on partial update

backend/internal/router/admin/applications.go

@@ -365,8 +365,12 @@ func handleUpdateApplication(c *gin.Context) {
 
 	fmt.Printf("更新应用前: ID=%d, EncryptType=%s, EncryptKey=%s\n", app.ID, app.EncryptType, app.EncryptKey)
 
-	app.Name = req.Name
-	app.Description = req.Description
+	if req.Name != "" {
+		app.Name = req.Name
+	}
+	if req.Description != "" {
+		app.Description = req.Description
+	}
 	if req.BillingType != "" {
 		app.BillingType = req.BillingType
 	}