迁移改号：000064-000067 顺延为 000065-000068，为 main 的 000064_ad_tracking 让号

- 000064_distribution_init -> 000065
- 000065_order_list_least_privilege -> 000066
- 000066_file_upload_owners -> 000067
- 000067_seed_test_distribution_site -> 000068
- 不改 SQL 内容，仅让 goose 版本号与 main 的迁移序列不重叠

backend/migrations/000067_file_upload_owners.sql

@@ -0,0 +1,17 @@
+-- +goose Up
+
+-- 私有文件上传归属：业务记录写入前，仅允许上传者预览自己的临时文件。
+CREATE TABLE file_upload_owners (
+  id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
+  user_id BIGINT UNSIGNED NOT NULL,
+  object_key VARCHAR(512) NOT NULL,
+  created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  PRIMARY KEY (id),
+  UNIQUE KEY uk_file_upload_owners_object_key (object_key),
+  KEY idx_file_upload_owners_user_id (user_id),
+  KEY idx_file_upload_owners_created_at (created_at)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='私有文件上传归属';
+
+-- +goose Down
+
+DROP TABLE IF EXISTS file_upload_owners;