fix(backend): handle relay-delivered Announce activities correctly

[sinoru]

What

リレーアクター経由で届いたAnnounceアクティビティを通常のRenoteと区別し、内包された元ノートをノートストリームに直接公開するように変更しました。

Changed the handling of Announce activities from relay actors so that the inner note is published directly to the notes stream, instead of being treated as a regular Renote.

Why

リレー経由で配信されたノートはリレーアクターのAnnounceで包まれているため、既存のロジックではRenoteとして表示されてしまう問題がありました。

Notes delivered through relays are wrapped in an Announce activity by the relay actor, causing them to appear as Renotes of the original instead of standalone notes.

Fix #11056

Additional info (optional)

リレーアクターの判定は、アクターのinboxまたはsharedInboxを承認済みリレーのエントリと照合して行います。

Relay actor detection works by matching the actor's inbox or sharedInbox against accepted relay entries.

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

[codecov]

Codecov Report

❌ Patch coverage is 13.79310% with 25 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.64%. Comparing base (c9c6ef2) to head (ef6936c).

Files with missing lines	Patch %	Lines
packages/backend/src/core/RelayService.ts	23.52%	13 Missing ⚠️
...ges/backend/src/core/activitypub/ApInboxService.ts	0.00%	12 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #17308      +/-   ##
===========================================
- Coverage    63.67%   63.64%   -0.04%     
===========================================
  Files         1162     1162              
  Lines       116490   116514      +24     
  Branches      8470     8454      -16     
===========================================
- Hits         74175    74154      -21     
- Misses       40110    40155      +45     
  Partials      2205     2205              

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[github-actions]

このPRによるapi.jsonの差分
差分はありません。
Get diff files from Workflow Page

[github-actions]

Backend memory usage comparison

Before GC

Metric	base (MB)	head (MB)	Diff (MB)	Diff (%)
VmRSS	330.13 MB	320.98 MB	-9.15 MB	-2.77%
VmHWM	330.13 MB	320.98 MB	-9.15 MB	-2.77%
VmSize	23124.85 MB	23114.71 MB	-10.13 MB	-0.04%
VmData	1394.90 MB	1384.40 MB	-10.50 MB	-0.75%

After GC

Metric	base (MB)	head (MB)	Diff (MB)	Diff (%)
VmRSS	330.27 MB	320.99 MB	-9.27 MB	-2.80%
VmHWM	330.27 MB	320.99 MB	-9.27 MB	-2.80%
VmSize	23124.94 MB	23115.13 MB	-9.80 MB	-0.04%
VmData	1394.98 MB	1384.82 MB	-10.16 MB	-0.72%

After Request

Metric	base (MB)	head (MB)	Diff (MB)	Diff (%)
VmRSS	330.51 MB	321.42 MB	-9.08 MB	-2.75%
VmHWM	330.51 MB	321.42 MB	-9.08 MB	-2.75%
VmSize	23124.94 MB	23115.21 MB	-9.72 MB	-0.04%
VmData	1394.90 MB	1384.90 MB	-10.00 MB	-0.71%

See workflow logs for details