feat: dependency injection and comments threads

[CodeVoyager]

Summary

• Inject CommentRepository as an optional last argument on admin and common comment services (defaulting to getCommentRepository(strapi)), so callers can swap the repository without changing service internals.
• Split admin posting into two methods: postComment creates a top-level admin comment (threadOf: null, related is the content relation), and postCommentThread replies in an existing thread. The existing route POST /moderate/thread/:id/postComment now calls postCommentThread, so the HTTP path for thread replies is unchanged.
• Expose blockNestedThreads on the admin service as a wrapper around modifiedNestedNestedComments.
• Update admin/common service tests to pass a mock repository and cover the new post/thread split.

Test plan

• Admin list, reports, thread details, approve, reject, update, and delete still work with the default repository (no injected repo).
• Posting a moderator reply via POST /moderate/thread/:id/postComment still creates a child comment (threadOf = that id), not a top-level comment.
• postComment (service) creates a top-level admin comment on the related entity.
• Blocking a nested thread via blockNestedThreads updates descendant blockedThread flags.
• Unit tests: admin.service, common.service, admin.controller.
• Confirm findAllInHierarchy response shape: the “pagination on comments tree” commit only changed tests to expect { data, pagination }, but the service still returns an array. Either restore the old assertions or wrap the tree in { data, pagination } before merge.

[codecov]

Codecov Report

❌ Patch coverage is 96.22642% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 99.33%. Comparing base (8384df8) to head (bfe78f1).

Files with missing lines	Patch %	Lines
server/src/services/admin/admin.service.ts	91.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #418      +/-   ##
==========================================
- Coverage   99.48%   99.33%   -0.15%     
==========================================
  Files          42       42              
  Lines        1353     1357       +4     
  Branches      316      336      +20     
==========================================
+ Hits         1346     1348       +2     
- Misses          7        9       +2     

Flag	Coverage Δ
unittest	99.33% <96.22%> (-0.15%)	⬇️

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