feat: implement deleteUser in Infra layer / Infra層のdeleteUser実装

[zigzagdev]

Motivation / 目的

Implement the repository layer for deleting user data as part of the User Delete API (#514).

ユーザー削除APIのInfra層（#515）として、ユーザーデータを削除するリポジトリ層を実装しました。

What I have done / 実施内容

• UserRepositroyInterface: deleteUser(int $id): void を追加
• UserRepository: deleteUser を実装
  • IDでユーザーを検索し、存在しない場合は Exception('User not found.') をスロー
  • delete() でレコードを削除
• UserRepositoryTest: DBインテグレーションテストを2件追加

Test Results / テスト結果

• test_deleteUser_removes_user_when_exists
• test_deleteUser_throws_exception_when_user_not_found

Closes #515

[zigzagdev]

Ok

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.01%. Comparing base (07483b1) to head (dd244d5).
⚠️ Report is 4 commits behind head on feat/user-delete.

Additional details and impacted files

@@                  Coverage Diff                   @@
##             feat/user-delete     #521      +/-   ##
======================================================
+ Coverage               59.94%   60.01%   +0.06%     
- Complexity               1515     1519       +4     
======================================================
  Files                     120      120              
  Lines                    7765     7778      +13     
======================================================
+ Hits                     4655     4668      +13     
  Misses                   3110     3110              

Files with missing lines	Coverage Δ
.../app/Packages/Domains/Tests/UserRepositoryTest.php	100.00% <100.00%> (ø)
src/app/Packages/Domains/UserRepository.php	97.43% <100.00%> (+0.37%)	⬆️

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