enhance: Embedded all attachment, renotes and discussion history into rss feed content & improve title (2025)

[CGsama]

What

The feed npm module dose not support multiple files, and enclosure format may not parse correct by apps, so that embedding all files into content. Also the email field is required by some app, so add a dummy one, could improved by use user email if have one.
The feed also can track back x posts for reply and renote, will include 10 most recent notes in the thread

Why

#7004

Additional info (optional)

Change originally made for #6696 at v11 and #8834 for v12, now for latest to match file structure, working fine on my instance (v11/v12/firefish) for years

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]

このPRによるapi.jsonの差分
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[codecov]

Codecov Report

Attention: Patch coverage is 5.30973% with 107 lines in your changes missing coverage. Please review.

Project coverage is 37.68%. Comparing base (297186e) to head (0636de6).
Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
packages/backend/src/server/web/FeedService.ts	5.30%	107 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #15353      +/-   ##
===========================================
- Coverage    38.70%   37.68%   -1.03%     
===========================================
  Files         1603     1603              
  Lines       204267   204369     +102     
  Branches      4015     3711     -304     
===========================================
- Hits         79067    77012    -2055     
- Misses      124594   126751    +2157     
  Partials       606      606              

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