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/route/app.php

@@ -3,6 +3,7 @@ declare(strict_types=1);
 
 use think\facade\Route;
 use app\api\controller\v1\Auth;
+use app\api\controller\v1\Platform;
 
 /**
  * API 应用路由
@@ -19,3 +20,8 @@ Route::group('v1/auth', function () {
     Route::post('logout', [Auth::class, 'logout']);
     Route::post('password', [Auth::class, 'password']);
 })->middleware(\app\api\middleware\Auth::class);
+
+// v1 平台账号管理接口（需登录）
+Route::group('v1/platform', function () {
+    Route::get('accounts', [Platform::class, 'accounts']);
+})->middleware(\app\api\middleware\Auth::class);