fix: delay before updating unread messages badge (WPB-23126)

[sbakhtiarov]

https://wearezeta.atlassian.net/browse/WPB-23126

https://wearezeta.atlassian.net/browse/WPB-23126

Issue:

Unread messages badge is not removed instantly when user closes a conversation after reading all messages.

Cause:

The app relies on UpdateConversationReadDateUseCase which has a 3-second debounce. If the user closes the conversation before debounce completes, the badge persists until the delayed update finishes.

Solution:

• Inject and call MarkConversationAsReadLocallyUseCase when leaving the conversation to immediately update the local read date
• Use DisposableEffect to handle all exit scenarios (back button, system gestures, navigation, etc.)
• Track the last read timestamp in MessageComposerViewModel and flush it on conversation close

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.67%. Comparing base (1092a3c) to head (0487629).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4557      +/-   ##
===========================================
+ Coverage    48.64%   48.67%   +0.02%     
===========================================
  Files          576      576              
  Lines        19950    19956       +6     
  Branches      3336     3337       +1     
===========================================
+ Hits          9705     9713       +8     
+ Misses        9218     9216       -2     
  Partials      1027     1027              

Files with missing lines	Coverage Δ
...conversations/composer/MessageComposerViewModel.kt	75.26% <100.00%> (+4.00%)	⬆️

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[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