refactor: improve conversation list rendering performance

[MohamadJaara]

Refactors conversation list item rendering to avoid doing UI-only and expensive work during paged item mapping. Search highlighting, legal-hold visibility, and currently playing audio state are now applied closer to rendering, reducing unnecessary remapping when those UI states change.

Also defers last-message markdown preview parsing to the UI layer and adds a lightweight markdown preview parser so conversation subtitles avoid full markdown parsing while preserving formatted previews.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

❌ Patch coverage is 55.91398% with 41 lines in your changes missing coverage. Please review.
✅ Project coverage is 51.19%. Comparing base (9341b52) to head (47174d4).

Files with missing lines	Patch %	Lines
...id/ui/markdown/LightweightMarkdownPreviewParser.kt	53.33%	6 Missing and 8 partials ⚠️
...ome/conversationslist/ConversationListViewModel.kt	44.44%	10 Missing ⚠️
...tions/usecase/GetConversationsFromSearchUseCase.kt	62.50%	4 Missing and 2 partials ⚠️
...i/home/conversationslist/model/ConversationItem.kt	33.33%	4 Missing ⚠️
...tlin/com/wire/android/mapper/ConversationMapper.kt	66.66%	2 Missing and 1 partial ⚠️
...wire/android/mapper/MessagePreviewContentMapper.kt	75.00%	2 Missing ⚠️
...lin/com/wire/android/ui/markdown/MarkdownParser.kt	66.66%	0 Missing and 2 partials ⚠️

❌ Your patch check has failed because the patch coverage (55.91%) 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             @@
##           develop    #4853      +/-   ##
===========================================
- Coverage    51.26%   51.19%   -0.08%     
===========================================
  Files          611      612       +1     
  Lines        21181    21172       -9     
  Branches      3405     3421      +16     
===========================================
- Hits         10859    10839      -20     
- Misses        9308     9318      +10     
- Partials      1014     1015       +1     

Files with missing lines	Coverage Δ
...wire/android/mapper/MessagePreviewContentMapper.kt	58.87% <75.00%> (+0.30%)	⬆️
...lin/com/wire/android/ui/markdown/MarkdownParser.kt	67.50% <66.66%> (-0.07%)	⬇️
...tlin/com/wire/android/mapper/ConversationMapper.kt	54.16% <66.66%> (+1.18%)	⬆️
...i/home/conversationslist/model/ConversationItem.kt	54.86% <33.33%> (-1.50%)	⬇️
...tions/usecase/GetConversationsFromSearchUseCase.kt	74.24% <62.50%> (-6.80%)	⬇️
...ome/conversationslist/ConversationListViewModel.kt	29.29% <44.44%> (-5.79%)	⬇️
...id/ui/markdown/LightweightMarkdownPreviewParser.kt	53.33% <53.33%> (ø)

... and 3 files with indirect coverage changes

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