fix(frontend): make the panel usable with screen readers (#6907)

* fix(frontend): make the panel usable with screen readers

* fix(frontend): keep mobile tab names and the inbound expiry hint

Review of #6907 found two gaps in the screen-reader pass:

- On phone-width screens catTabLabel renders only the icon and names the
  tab by putting aria-label on it, but callers now pass that icon with
  aria-hidden for the desktop label, so every Settings, Xray and Host
  category tab lost its name under TalkBack. catTabLabel now clears
  aria-hidden on the icon it uses as the name.
- DateTimePicker forwarded id and aria-label but not aria-describedby,
  so the inbound expiry hint ("leave blank to never expire") was never
  attached. It now forwards it on both the Gregorian and Jalali input.

frontend/src/test/language-scope.test.ts

@@ -19,6 +19,7 @@ describe('subscription language scope', () => {
     const getLanguage = vi.spyOn(utils.LanguageManager, 'getLanguage');
     const reload = vi.fn();
     vi.stubGlobal('window', { navigator: { language: 'en-US' }, location: { reload } });
+    vi.stubGlobal('document', { documentElement: {} });
 
     const { readyI18n } = await import('@/i18n/react');
     expect(getLanguage).not.toHaveBeenCalled();