已完成用户APP首期功能开发

交付用户端首期页面、配套接口、后台资源及测试文档。用户APP构建、静态分析和三个管理后台构建通过；完整测试仍有2项失败，后端模型注释检查未通过，详见交付记录。

backend/api/internal/logic/gas/ticket_values.go

@@ -5,6 +5,7 @@ package gas
 var supportedTicketCategories = map[string]struct{}{
 	"delivery": {}, "installation": {}, "repair": {},
 	"inspection": {}, "reinspection": {}, "customer_service": {},
+	"contract_change": {},
 }
 
 var supportedTicketPriorities = map[string]struct{}{