feat: use new credentials manager API for AnkiWeb passwords

[BrayanDSO]

On top of #21770

Approach

In the commits

How Has This Been Tested?

Galaxy Tab S9, Android 16, Samsung Password manager

Screen_Recording_20260906_140426_AnkiDroid.mp4

Emulator 28, with no credentials manager installed

Screen_recording_20260906_111636.webm

Learning (optional, can help others)

https://developer.android.com/identity/credential-manager

https://developer.android.com/reference/kotlin/androidx/credentials/package-summary

Checklist

Please, go through these checks before submitting the PR.

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner