feat(platform): add endpoint to retrieve platform accounts for a user

- Introduced `getPlatformAccountsByUserId` method in `DyVideoUser` model to fetch active platform accounts for a specified user.
- Added new API route for accessing platform accounts under `v1/platform/accounts`, requiring user authentication.

app/api/model/DyVideoUserTitk.php

@@ -0,0 +1,33 @@
+<?php
+declare(strict_types=1);
+
+namespace app\api\model;
+
+use think\Model;
+
+/**
+ * TikTok 账号附表模型（对应 dy_video_user_titk 表）
+ *
+ * 该表在 acgpmw 平台账号管理页用于补充 TikTok 账号的国家信息。
+ */
+class DyVideoUserTitk extends Model
+{
+    protected $connection = 'dbmember';
+
+    protected $name = 'dy_video_user_titk';
+
+    protected $pk = 'id';
+
+    protected $autoWriteTimestamp = false;
+
+    /**
+     * 根据授权账号 ID 获取 TikTok 附加信息。
+     *
+     * @param int $vuid 授权账号主表 ID
+     * @return self|null
+     */
+    public static function findByVuid(int $vuid): ?self
+    {
+        return self::where('vuid', $vuid)->find();
+    }
+}