fix(authenticator): Add accessible names for password toggle and form errors

[VarshithaPamisetty]

Issue #, if available:
Fixes #6568
Fixes #6581

Description:
Continues the work in #6577 by @ekjotmultani, addressing the review feedback.

Adds tooltip/accessible names to the password visibility toggle so screen readers announce "Show password"/"Hide password" (#6568), and wraps banner and form content in semantics so validation errors are announced (#6581).

Review follow-ups from #6577:

• Tooltip strings are defined in the ARB source (inputs_en.arb) and reflected in the generated localizations.

Tests

• Added widget tests for the password toggle accessible name (Show/Hide) and the banner/snackbar live-region announcements.
• Full authenticator suite passes locally; dart analyze and dart format clean.
• Manually verified with VoiceOver on web (Chrome): the toggle announces "Show password" / "Hide password", and submitting an empty form auto-announces the validation error via the live-region.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 86.20690% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 41.25%. Comparing base (a6ec724) to head (cfbde09).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7254      +/-   ##
==========================================
+ Coverage   40.98%   41.25%   +0.26%     
==========================================
  Files         121      121              
  Lines        8273     8288      +15     
  Branches     3598     3604       +6     
==========================================
+ Hits         3391     3419      +28     
+ Misses       4882     4869      -13     

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[cadivus]

Where does this new gap between "Password" and "Confirm Password" come from? I think it looks a bit odd.

[cadivus]

Where does this new gap between "Password" and "Confirm Password" come from? I think it looks a bit odd.

Is it eventually caused by the empty helper text? If so, how about setting https://api.flutter.dev/flutter/material/InputDecoration/helperStyle.html to make the font small (1? even 0?).

[VarshithaPamisetty]

Yes, it's from the "helperText: ' '" workaround. I'll try your helperStyle suggestion to collapse the gap and confirm VoiceOver still announces the error, then update.

[VarshithaPamisetty]

Yes, it's from the "helperText: ' '" workaround. I'll try your helperStyle suggestion to collapse the gap and confirm VoiceOver still announces the error, then update.

Removed the helperText workaround entirely. The gap is gone, and errors are still announced via the banner/snackbar liveRegion (verified with VoiceOver on web)