feat: implement Presentation layer for DELETE /api/v1/users/{id} / ユーザー削除APIのPresentation層実装

[zigzagdev]

Motivation / 目的

Implement the Controller and route for the User Delete API as part of #514.

ユーザー削除APIのPresentation層（#517）として、ControllerとRouteを実装しました。

What I have done / 実施内容

• UserController::deleteUser(): route {id} を int にキャストして DeleteUserUseCase を呼び出す
  • 200 on success
  • 404 when 'User not found.' exception is thrown
  • 500 on other errors with Log::error
• Route: DELETE /api/v1/users/{id}

Test Results / テスト結果

Integration tests hitting the real DB and HTTP endpoint:

• test_delete_user_returns_200_when_user_exists
• test_delete_user_returns_404_when_user_not_found

Closes #517

[codecov]

Codecov Report

❌ Patch coverage is 85.18519% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.30%. Comparing base (6f93265) to head (195533f).
⚠️ Report is 4 commits behind head on feat/user-delete.

Files with missing lines	Patch %	Lines
...pp/Packages/Features/Controller/UserController.php	57.89%	8 Missing ⚠️

Additional details and impacted files

@@                  Coverage Diff                   @@
##             feat/user-delete     #523      +/-   ##
======================================================
+ Coverage               60.12%   60.30%   +0.17%     
- Complexity               1524     1534      +10     
======================================================
  Files                     122      123       +1     
  Lines                    7800     7854      +54     
======================================================
+ Hits                     4690     4736      +46     
- Misses                   3110     3118       +8     

Files with missing lines	Coverage Δ
src/app/Packages/Features/Tests/DeleteUserTest.php	100.00% <100.00%> (ø)
...pp/Packages/Features/Controller/UserController.php	79.74% <57.89%> (-6.92%)	⬇️

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