fix: show invalid credentials error on login screens [WPB-14814]

[Garzas]

https://wearezeta.atlassian.net/browse/WPB-14814

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PR Submission Checklist for internal contributors

• The PR Title

  • conforms to the style of semantic commits messages¹ supported in Wire's Github Workflow²
  • contains a reference JIRA issue number like SQPIT-764
  • answers the question: If merged, this PR will: ... ³

• The PR Description

  • is free of optional paragraphs and you have filled the relevant parts to the best of your ability

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What's new in this PR?

• Shows a persistent invalid credentials error on the login screen after the dialog is dismissed
• Applies the same error marking to both old and new email/password login flows
• Keeps the message generic to avoid revealing whether the email/username or password was incorrect
• Clears the inline error once the user edits the login input
• Adds ViewModel coverage for preserving and clearing the error state

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 49.14%. Comparing base (5d7e15a) to head (3cd2150).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4903      +/-   ##
===========================================
+ Coverage    49.12%   49.14%   +0.01%     
===========================================
  Files          650      650              
  Lines        22983    22989       +6     
  Branches      3516     3518       +2     
===========================================
+ Hits         11291    11297       +6     
  Misses       10645    10645              
  Partials      1047     1047              

Files with missing lines	Coverage Δ
...d/ui/authentication/login/email/LoginEmailState.kt	100.00% <100.00%> (ø)
.../authentication/login/email/LoginEmailViewModel.kt	79.25% <100.00%> (+0.56%)	⬆️

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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