实现快传，完善快传和网盘的功能，实现文件的互传等一系列功能

backend/src/main/java/com/yoyuzh/transfer/CreateTransferSessionRequest.java

@@ -0,0 +1,12 @@
+package com.yoyuzh.transfer;
+
+import jakarta.validation.Valid;
+import jakarta.validation.constraints.NotEmpty;
+
+import java.util.List;
+
+public record CreateTransferSessionRequest(
+        @NotEmpty(message = "至少选择一个文件")
+        List<@Valid TransferFileItem> files
+) {
+}