[backend] Add automatic cleanup of old news feed items (#15643)

[Antoine-Quintin]

Proposed changes

• New cleanOldNewsFeedItems(context, user, cutoffDate) function in news-feed-domain.ts that deletes locally cached NewsFeedItem entities older than the cutoff. Uses elPaginate + promiseMap with concurrency 5, aligned with the pattern used in loadAndSaveLatestNewsFeed and [backend/frontend] feat(news-feed): mark items as read on list page load (#15934) #15960.
• Cleanup invocation added in hubRegistrationManager, called after loadAndSaveLatestNewsFeed at each tick (every hour), wrapped in its own try/catch so a cleanup failure doesn't break the manager.
• New configuration keys hub_registration_manager:news_feed_cleanup_interval_value (default 180) and hub_registration_manager:news_feed_cleanup_interval_unit (default "days"). Pattern reuses the value + unit approach from the existing retentionManager for flexibility (days / hours / minutes / seconds — adjustable without code change).
• Continues the cleanup of free-string filters started in [backend/frontend] feat(news-feed): mark items as read on list page load (#15934) #15960 by using FilterMode.And and FilterOperator.Lt enums explicitly.
• 4 new unit tests in newsFeed-test.ts covering filter construction, batch deletion, empty case, and resilience to ALREADY_DELETED_ERROR.

Related issues

• Closes Cleanup old newsfeed (older than 6 months) #15643
• Related to 🎯 Cleanup old news (older than 6 months) OCTI  FiligranHQ/xtm-hub#2197
• Companion PR on XTM Hub: [backend] feat(news-feed): add scheduled cleanup of expired items (#2197) FiligranHQ/xtm-hub#2325

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case (coverage and e2e)
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

[codecov]

Codecov Report

❌ Patch coverage is 78.43137% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 35.80%. Comparing base (71b54d9) to head (76d4b20).
⚠️ Report is 23 commits behind head on master.

Files with missing lines	Patch %	Lines
...ncti-graphql/src/manager/hubRegistrationManager.ts	57.50%	17 Missing ⚠️
.../src/modules/xtm/hub/news-feed/news-feed-domain.ts	91.93%	5 Missing ⚠️

❌ Your patch check has failed because the patch coverage (78.43%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #16018      +/-   ##
==========================================
+ Coverage   34.49%   35.80%   +1.31%     
==========================================
  Files        3254     3278      +24     
  Lines      220156   227505    +7349     
  Branches    40877    43750    +2873     
==========================================
+ Hits        75935    81468    +5533     
- Misses     144221   146037    +1816     

Flag	Coverage Δ
opencti-client-python	46.36% <ø> (ø)
opencti-front	4.06% <ø> (+0.64%)	⬆️
opencti-graphql	73.15% <78.43%> (+1.83%)	⬆️

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