fix: Fix alignment issues of app password form

[sandicej]

• Resolves: [Bug]: Alignment issues of app password form #52171

Summary

Set form max-width to 400px for consistency with other settings forms.
Moved "Create new app password" to a new line to align with the styling of other forms.

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Before fix:

After fix:

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)