feat(settings): show attention indicator on tabs and update cards

[andrebrait]

Summary

When an OMP version update (or app self-update) is available, the Settings gear button in the sidebar displays an attention dot. However, navigating into Settings previously showed no indication of why attention was needed or which section to look at.

This PR treats the attention dot as a generic signal and propagates it to:

1. The Settings section tab (SettingsTabs): adds an attentionTabs?: Partial<Record<SettingsTab, boolean | string>> prop. Renders a matching accent attention dot on the tab icon (in both vertical and horizontal mobile layouts) with accessible name / role="status" announcements.
2. The Settings cards inside the System tab (SettingsConfig): adds the attention dot next to the "OMP CLI & Runtime" and "omp-web Desktop & UI" card headings along with accented border styling when an update is available.
3. Passes ompUpdateAvailable down from AppShell to SettingsConfig so the System tab immediately reflects attention status upon opening.

Test Plan

• Tested vertical and horizontal SettingsTabs rendering with attentionTabs present and omitted (SettingsTabs.test.mjs).
• Verified aria-label and role="status" accessibility attributes on both layouts.
• Verified typecheck with tsc --noEmit and linter with npm run lint.
• Ran full unit test suite (812 tests passing).