fix(upload): 分片改 POST 并放宽 Nginx 反代，避免 PUT 大 body 断连

- 管理端分片请求改为 POST；后端同时保留 PUT
- /api/ 增加 proxy_request_buffering off；CORS Allow-Headers 略扩展

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）
+// 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。
 func PutMultipartChunk(c *gin.Context) {
 	siteID := c.Param("site_id")
 	uploadID := c.Param("upload_id")

server/main.go

@@ -99,7 +99,7 @@ func main() {
 			c.Header("Access-Control-Allow-Origin", "*")
 		}
 		c.Header("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
-		c.Header("Access-Control-Allow-Headers", "Content-Type, Authorization")
+		c.Header("Access-Control-Allow-Headers", "Content-Type, Authorization, Accept, Origin, X-Requested-With")
 		if c.Request.Method == "OPTIONS" {
 			c.AbortWithStatus(http.StatusNoContent)
 			return
@@ -174,6 +174,8 @@ func main() {
 		admin.POST("/sites/:site_id/assets", handlers.RequirePermission(models.PermModuleUpload), handlers.UploadSiteAsset)
 		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)