- ChronikFuerDichBox: move update() inside the failure branch so success
path skips it, matching NotificationDropdown's pattern
- NotificationDropdown test: add role=alert assertion for mark-all-read
failure to match existing dismiss-failure coverage in ChronikFuerDichBox
- +page.server.ts: use getErrorMessage(undefined) instead of null so the
missing-notificationId 400 goes through the same i18n pipeline as other errors
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>