chore: clear pre-commit eslint warnings (unused symbols, stale disables, test any)

Cleans up the lint warnings the pre-commit hook surfaces, without any
behavioral change:

- Remove unused imports/vars/destructured props (parseISO, useEffect,
  format, durMin, roles, daysInYear, ALLOWED_PLUGIN_FILES, continuesBefore,
  isPushConnected, isSelected) and the now-unused parseDuration import.
- Drop three stale `// eslint-disable-next-line no-undef` directives that
  no longer suppress anything (browser-navigation, smime/crypto-engine).
- recurrence-expansion.test.ts: replace 39 `as any` casts with a cast-only
  `rule()` helper for partial recurrence-rule fixtures, typed access to
  utcStart/utcEnd (now on CalendarEvent), and the source's
  `Partial<CalendarEvent> & { excluded?: boolean }` for the excluded
  override. No defaults are injected, so the expansion logic sees the same
  partial rules as before (35 tests still green).

Remaining: 7 react-hooks/exhaustive-deps warnings are left as-is — adding
the missing deps changes effect/memo timing and needs per-hook review, not
a mechanical fix. tsc --noEmit clean; eslint 0 errors / 7 warnings.

lib/birthday-calendar.ts

@@ -1,6 +1,6 @@
 import type { ContactCard, CalendarEvent, Calendar, PartialDate, Timestamp } from '@/lib/jmap/types';
 import { getContactDisplayName } from '@/stores/contact-store';
-import { format, eachYearOfInterval, parseISO } from 'date-fns';
+import { eachYearOfInterval, parseISO } from 'date-fns';
 
 export const BIRTHDAY_CALENDAR_ID = '__birthday-calendar__';
 export const BIRTHDAY_CALENDAR_COLOR = '#eab308'; // Yellow