fix(upload): 分片用 multipart 字段 chunk、路由顺序与串行上传

- 前端 FormData+chunk，避免 raw body 被中间层断连
- Gin 分片路由置于 POST .../assets 之前
- 分片并发降为 1

Made-with: Cursor

server/handlers/multipart_upload.go

@@ -215,7 +215,7 @@ func MultipartUploadStatus(c *gin.Context) {
 	})
 }
 
-// PutMultipartChunk 上传单个分片（二进制 body，长度须与分片大小一致）。路由同时注册 POST 与 PUT，建议客户端用 POST。
+// PutMultipartChunk 上传单个分片。支持 multipart 字段 chunk（推荐）或 application/octet-stream 原始 body；路由同时注册 POST 与 PUT。
 func PutMultipartChunk(c *gin.Context) {
 	siteID := c.Param("site_id")
 	uploadID := c.Param("upload_id")
@@ -252,7 +252,38 @@ func PutMultipartChunk(c *gin.Context) {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": "创建临时文件失败"})
 		return
 	}
-	n, err := io.Copy(f, io.LimitReader(c.Request.Body, expected+1))
+
+	ct := strings.ToLower(c.GetHeader("Content-Type"))
+	var src io.Reader
+	if strings.HasPrefix(ct, "multipart/form-data") {
+		// 与整文件上传一致走 multipart，避免部分网关对 raw POST body 断连
+		fh, err := c.FormFile("chunk")
+		if err != nil {
+			_ = f.Close()
+			_ = os.Remove(tmp)
+			c.JSON(http.StatusBadRequest, gin.H{"error": "请使用表单字段 chunk 上传分片"})
+			return
+		}
+		if fh.Size > 0 && fh.Size != expected {
+			_ = f.Close()
+			_ = os.Remove(tmp)
+			c.JSON(http.StatusBadRequest, gin.H{"error": "分片大小不符"})
+			return
+		}
+		part, err := fh.Open()
+		if err != nil {
+			_ = f.Close()
+			_ = os.Remove(tmp)
+			c.JSON(http.StatusBadRequest, gin.H{"error": "打开分片失败"})
+			return
+		}
+		defer part.Close()
+		src = part
+	} else {
+		src = c.Request.Body
+	}
+
+	n, err := io.Copy(f, io.LimitReader(src, expected+1))
 	_ = f.Close()
 	if err != nil {
 		_ = os.Remove(tmp)

server/main.go

@@ -171,14 +171,14 @@ func main() {
 		admin.PUT("/sites/:site_id/homepage", handlers.RequirePermission(models.PermHomepageEdit), handlers.UpdateHomepage)
 		admin.GET("/sites/:site_id/assets/downloadable", handlers.RequirePermission(models.PermHomepageEdit), handlers.ListDownloadableAssets)
 		admin.GET("/sites/:site_id/assets", handlers.RequirePermission(models.PermSiteManage), handlers.ListSiteAssets)
-		admin.POST("/sites/:site_id/assets", handlers.RequirePermission(models.PermModuleUpload), handlers.UploadSiteAsset)
+		// 分片路由须在 POST .../assets 整文件上传之前注册，避免被更泛的路由误匹配
 		admin.POST("/sites/:site_id/assets/init-multipart", handlers.RequirePermission(models.PermModuleUpload), handlers.InitMultipartUpload)
 		admin.GET("/sites/:site_id/assets/multipart/:upload_id/status", handlers.RequirePermission(models.PermModuleUpload), handlers.MultipartUploadStatus)
-		// 分片用 POST：部分反向代理对 PUT + 大 body 会断连，浏览器表现为 Network Error
 		admin.POST("/sites/:site_id/assets/multipart/:upload_id/chunk/:chunk_index", handlers.RequirePermission(models.PermModuleUpload), handlers.PutMultipartChunk)
 		admin.PUT("/sites/:site_id/assets/multipart/:upload_id/chunk/:chunk_index", handlers.RequirePermission(models.PermModuleUpload), handlers.PutMultipartChunk)
 		admin.POST("/sites/:site_id/assets/multipart/:upload_id/complete", handlers.RequirePermission(models.PermModuleUpload), handlers.CompleteMultipartUpload)
 		admin.DELETE("/sites/:site_id/assets/multipart/:upload_id", handlers.RequirePermission(models.PermModuleUpload), handlers.AbortMultipartUpload)
+		admin.POST("/sites/:site_id/assets", handlers.RequirePermission(models.PermModuleUpload), handlers.UploadSiteAsset)
 		admin.POST("/sites/:site_id/folders", handlers.RequirePermission(models.PermModuleUpload), handlers.CreateSiteFolder)
 		admin.DELETE("/sites/:site_id/assets/:asset_id", handlers.RequirePermission(models.PermSiteManage), handlers.DeleteSiteAsset)
 		admin.GET("/sites", handlers.RequirePermission(models.PermSiteManage), handlers.GetSites)