- App.tsx: replace the inline `style={{}}` on the re-auth banner wrapper with
Mantine style props (pos/top/bg) plus a `.reauth-banner-bar` class for the
z-index/box-shadow that have no Mantine shorthand.
- App.tsx: extract the ~100-line inline `onAuthorize` and the inline `onCancel`
step-up handlers into named `handleStepUpAuthorize`/`handleStepUpCancel`.
- ReAuthBanner: move the flat `styles={{ root }}` (background/border) into a
`reauth` Alert theme variant; replace the raw `<span>` with `<Text>`.
- StepUpAuthModal: extract the inline `onClick` wrapper into `handleAuthorize`.
No behavior change; validate + integration green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DZyeWManYTvcXxjcrhxSQc
