fix: Use PHP_AUTH_PW for strict password confirmation

[SystemKeeper]

• Resolves: [Bug]: Creating and deleting App Tokens runs into error #62190

Summary

We already make sure that AUTHORIZATION headers are copied to PHP_AUTH_USER and PHP_AUTH_PW, so these should work in all cases.
Please check if there's any reason to access the raw authorization header in that method, in that case we could use the PHP_AUTH_* ones as fallback.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI