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/smime/crypto-engine.ts

@@ -225,7 +225,6 @@ class Pkcs12CryptoEngine extends pkijs.CryptoEngine {
     const cryptoKey = await this.importKey(
       'raw',
       keyData,
-      // eslint-disable-next-line no-undef
       { name: algName, length: keyLen * 8 } as Algorithm,
       false,
       ['decrypt'],
@@ -234,7 +233,6 @@ class Pkcs12CryptoEngine extends pkijs.CryptoEngine {
     // Decrypt
     const ciphertext = parameters.encryptedContentInfo.getEncryptedContent();
     return this.decrypt(
-      // eslint-disable-next-line no-undef
       { name: algName, iv: ivBytes } as Algorithm,
       cryptoKey,
       ciphertext,