feat: add GET /api/v1/user/me endpoint / ログイン中ユーザー取得APIの追加

[zigzagdev]

Motivation / 目的

AuthController::login のレスポンスはトークンのみでユーザーのidを返さないため、フロントエンドはログイン後に「自分自身」の情報を取得する手段を持っていなかった。これがマイページ表示ができない一因だった (#542)。

The login response only returns a token, never the user's id, so the frontend had no way to fetch "its own" user data after logging in. This was one of the causes preventing mypage from displaying (#542).

Closes #542

What I have done / 実施内容

• routes/api.php に GET /v1/user/me を auth:sanctum ミドルウェア付きで追加
• AuthController::me を追加し、Sanctumが認証済みリクエストから解決したユーザーのidを既存の GetUserByIdUseCase に渡して結果を返す
• Domain層・Infra層は既存の findById を、Application層は既存の GetUserByIdUseCase をそのまま再利用（変更なし）。今回の変更はPresentation層のみ (feat: implement Presentation layer for GET /api/v1/user/me / ログイン中ユーザー取得APIのPresentation層実装 #543)

Test Results / テスト結果

• test_me_returns_200_with_authenticated_user_when_authenticated
• test_me_returns_401_when_unauthenticated
• test_me_returns_500_on_unexpected_error
• 既存の LoginTest / LogoutTest の回帰なしを確認済み

[codecov]

Codecov Report

❌ Patch coverage is 94.80519% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.51%. Comparing base (0ea56e1) to head (3af3152).

Files with missing lines	Patch %	Lines
...pp/Packages/Features/Controller/AuthController.php	80.00%	4 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##             feat/user     #544      +/-   ##
===============================================
+ Coverage        62.21%   62.51%   +0.30%     
- Complexity        1604     1615      +11     
===============================================
  Files              135      136       +1     
  Lines             8252     8329      +77     
===============================================
+ Hits              5134     5207      +73     
- Misses            3118     3122       +4     

Files with missing lines	Coverage Δ
src/app/Packages/Features/Tests/MeTest.php	100.00% <100.00%> (ø)
...pp/Packages/Features/Controller/AuthController.php	93.22% <80.00%> (-6.78%)	⬇️

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