[PM-43140] fix(browser): detect old password fields in change forms

[tmsteph]

🎟️ Tracking

Relates to #1620

📔 Objective

Password-change and password-expiry forms commonly use fields such as oldPassword, currentPassword, newPassword, and a confirmation field.

Bitwarden already has change-password notification logic for password + newPassword, but the current-password classifier only recognized spaced phrases such as current password. Compact field names like oldPassword or currentPassword therefore could fall through classification on multi-password forms and never be captured as the current password.

Add conservative current-password / old-password keyword variants to the password-update classifier. Bitwarden's existing tokenizer removes hyphens, so these variants match compact field names (currentPassword, oldPassword) without broad fuzzy matching.

The regression test covers an expired/change-password style form with oldPassword, newPassword, and confirmation fields and verifies that the old-password field is classified as CurrentPasswordUpdate.

Validation:

• git diff --check
• patch applies cleanly to current main
• verified tokenizer behavior: old-password -> oldpassword, matching oldPassword

I did not run the full browser test suite locally because the monorepo dependency install previously exhausted the available worker resources. CI can provide full project validation.

📸 Screenshots

Not applicable. This changes form-field classification only and reuses Bitwarden's existing change-password UI/notification flow.

[bitwarden-bot]

Thank you for your contribution! We've added this to our internal tracking system for review.
ID: PM-43140
Link: https://bitwarden.atlassian.net/browse/PM-43140

Details on our contribution process can be found here: https://contributing.bitwarden.com/contributing/pull-requests/community-pr-process.