fetch(add): 新增

src/api/BaseService.ts

@@ -170,16 +170,16 @@ export class BaseService {
 
     if (params) {
       Object.keys(params).forEach((key) => {
-        formData.append(key, params[key])
+        if (params[key] !== undefined && params[key] !== null && params[key] !== '') {
+          formData.append(key, String(params[key]))
+        }
       })
     }
 
+    // 不要手动设置 Content-Type,让浏览器自动设置(包含正确的 boundary)
     return request.post<BaseResponse<T>>({
       url,
-      data: formData,
-      headers: {
-        'Content-Type': 'multipart/form-data'
-      }
+      data: formData
     })
   }