feat: refactor request body handling to use BodyStorage for improved efficiency

common/body_storage.go

@@ -302,6 +302,12 @@ func CreateBodyStorageFromReader(reader io.Reader, contentLength int64, maxBytes
 	return storage, nil
 }
 
+// ReaderOnly wraps an io.Reader to hide io.Closer, preventing http.NewRequest
+// from type-asserting io.ReadCloser and closing the underlying BodyStorage.
+func ReaderOnly(r io.Reader) io.Reader {
+	return struct{ io.Reader }{r}
+}
+
 // CleanupOldCacheFiles 清理旧的缓存文件（用于启动时清理残留）
 func CleanupOldCacheFiles() {
 	// 使用统一的缓存管理