fix(backend): Inboxのエラーをthrowせずreturnしている問題を修正

[kakkokari-gtyih]

What

Fixes a type confusion bug where exceptions are incorrectly returned instead of thrown. The calling code will attempt to process the Error as an Activity, causing it to fail with cryptic and confusing errors.

Why

Fix https://activitypub.software/TransFem-org/Sharkey/-/issues/796
エラーがエラーとしてログに残るようになる

Additional info (optional)

Checklist

• Read the contribution guide
• Test working in a local environment
• (If needed) Add story of storybook
• (If needed) Update CHANGELOG.md
• (If possible) Add tests

[github-actions]

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[codecov]

Codecov Report

Attention: Patch coverage is 11.11111% with 8 lines in your changes missing coverage. Please review.

Project coverage is 39.86%. Comparing base (c1f19fa) to head (d7e7b9a).
Report is 6 commits behind head on develop.

Files with missing lines	Patch %	Lines
...ges/backend/src/core/activitypub/ApInboxService.ts	11.11%	8 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #15022      +/-   ##
===========================================
- Coverage    39.98%   39.86%   -0.12%     
===========================================
  Files         1563     1563              
  Lines       197737   197741       +4     
  Branches      3644     3633      -11     
===========================================
- Hits         79056    78835     -221     
- Misses      118077   118299     +222     
- Partials       604      607       +3     

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[syuilo]

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