a11y(dialogs): full keyboard operability

[unajiogenyi05-hub]

• Fix ConfirmDialog cancel button: add focus-visible ring (was unstyled)
• Fix ConfirmDialog confirm button: tone-aware ring (blue default / red destructive) replacing the broken primary-600 token
• Enable restoreFocus in useDialogFocusTrap so trigger regains focus after dialog closes (WCAG 2.1 SC 3.2.2)
• Add ConfirmDialogKeyboard.test.tsx with 21 tests covering: tab order, wrap forward/backward, Enter/Space activation, Escape from any position, focus restoration, focus-visible classes, and destructive tone keyboard flow

Description

Closes #

Type of Change

• Bug fix (non-breaking change that resolves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Refactor (no functional change, internal code improvement)
• Documentation update

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Pre-flight Checklist

All items must be checked before requesting review.

• npm run lint passes with no errors
• npm test passes with no failures
• npm run build completes successfully

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Testing & Coverage

• Module test coverage for impacted files meets or exceeds the 95% minimum threshold
  (run npm test -- --coverage and check the per-file table)
• If this PR adds or modifies UI components, accessibility tests were written using
  the shared utilities in src/test-utils/a11y.tsx

What was tested?

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Accessibility & Security Notes

Accessibility

Security

closes #638

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