refactor: Reduce message list mapping and ViewModel scope overhead

[MohamadJaara]

Summary

• Defer markdown parsing for text messages to the UI layer instead of doing it during message mapping
• Cache mention display mapping across recompositions and lazily compute formatted message timestamps
• Limit scoped audio and asset local path ViewModel keys to the visible message window plus a small prefetch buffer
• Keep the currently playing audio message in scope while playback is active

Testing

• Added regression coverage for deferring markdown document parsing

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
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 75.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 51.23%. Comparing base (47174d4) to head (3561303).

Files with missing lines	Patch %	Lines
...wire/android/mapper/RegularMessageContentMapper.kt	50.00%	1 Missing ⚠️
...e/android/ui/home/conversations/model/UIMessage.kt	83.33%	0 Missing and 1 partial ⚠️

❌ Your patch check has failed because the patch coverage (75.00%) 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                                      @@
##           mo/refactor/markdown-formating-while-mapping-conversaions    #4857      +/-   ##
=============================================================================================
+ Coverage                                                      51.19%   51.23%   +0.03%     
=============================================================================================
  Files                                                            612      612              
  Lines                                                          21172    21188      +16     
  Branches                                                        3421     3421              
=============================================================================================
+ Hits                                                           10839    10855      +16     
+ Misses                                                          9318     9316       -2     
- Partials                                                        1015     1017       +2     

Files with missing lines	Coverage Δ
...ndroid/ui/home/conversations/model/MessageTypes.kt	14.28% <ø> (ø)
...wire/android/mapper/RegularMessageContentMapper.kt	17.12% <50.00%> (-1.40%)	⬇️
...e/android/ui/home/conversations/model/UIMessage.kt	40.68% <83.33%> (+0.74%)	⬆️

... and 3 files with indirect coverage changes

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