feat: implement Infra layer for favorite heritages list API / お気に入り一覧APIのInfra層実装

[zigzagdev]

Motivation / 目的

Add the Infra layer support needed for a "list my favorite heritages" API: a way to fetch the world heritage site ids a user has favorited, reusing the existing favorites() relation added for addFavorite().

What I have done / 実施内容

• Added FavoriteRepositoryInterface::getFavoriteWorldHeritageIds(int $userId): array
• Implemented it in FavoriteRepository, returning world heritage site ids ordered by most recently favorited first, throwing Exception('User not found.') when the user doesn't exist (same convention as addFavorite)
• Added withTimestamps() to User::favorites() so pivot created_at is populated on attach(), which the new method orders by
• Added integration tests against the real test database

Test Results / テスト結果

• test_getFavoriteWorldHeritageIds_returns_ids_ordered_by_most_recently_favorited
• test_getFavoriteWorldHeritageIds_returns_empty_array_when_no_favorites
• test_getFavoriteWorldHeritageIds_throws_exception_when_user_not_found

Closes #566

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.70%. Comparing base (c293a43) to head (b4acd34).

Additional details and impacted files

@@                   Coverage Diff                    @@
##             feat/user-favorite     #564      +/-   ##
========================================================
+ Coverage                 63.59%   63.70%   +0.10%     
- Complexity                 1652     1657       +5     
========================================================
  Files                       142      142              
  Lines                      8582     8607      +25     
========================================================
+ Hits                       5458     5483      +25     
  Misses                     3124     3124              

Files with missing lines	Coverage Δ
src/app/Models/User.php	100.00% <100.00%> (ø)
...p/Packages/Domains/Favorite/FavoriteRepository.php	100.00% <100.00%> (ø)
.../Domains/Favorite/Tests/FavoriteRepositoryTest.php	100.00% <100.00%> (ø)

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[zigzagdev]

OK