add backend

backend/src/main/java/com/yoyuzh/files/FileMetadataResponse.java

@@ -0,0 +1,14 @@
+package com.yoyuzh.files;
+
+import java.time.LocalDateTime;
+
+public record FileMetadataResponse(
+        Long id,
+        String filename,
+        String path,
+        long size,
+        String contentType,
+        boolean directory,
+        LocalDateTime createdAt
+) {
+}