#4908 feat: filter keyboard shortcut settings

[!TIP]
PR walkthrough: Open the visual walkthrough

Finding an action to rebind requires scanning the entire keyboard shortcut list. An inline label filter narrows core and integration rows while preserving unsaved edits and conflict warnings.

Validation

• Mounted card: 14 Vitest tests, including filtering, draft retention, hidden conflict peers and keyboard focus recovery.
• Focused ESLint, TypeScript typecheck, i18n checks, public-doc and specification validators.
• Production E2E builds followed by Chromium (2 tests, including a 767px fine-pointer viewport) and mobile-chrome (1 test), one worker and zero retries.
• Inspected desktop and phone screenshots and measured search and clear controls.

Checklist

• If I do not have repository write access and this is a large architectural change, I discussed the direction in a linked issue before opening this PR.
• This PR contains one logical change; unrelated work is split into separate PRs.
• I have performed a self-review of my code.
• I have manually tested my changes and they work as expected.
• My changes have tests that cover the new functionality and edge cases.
• If my change touches UI files (apps/web/), I have added or updated Playwright e2e tests in apps/web/e2e/ and verified them with make test-e2e.
• I checked whether this affects public docs in docs/public/** and updated them or noted why no docs change is needed.

Screenshots