Calendar: add events (NE Hub calendar + iCloud) and a Podcast tab

- Add, edit and delete events; month/agenda views open them on tap
- NE Hub calendar stored on the server and published as a private ICS subscribe link
- iCloud CalDAV read/write with an app-specific password (encrypted at rest,
  only *.icloud.com contacted, event addresses checked against the calendar)
- Edits patch the existing entry so alarms/attendees survive; writes use If-Match / If-None-Match
- Time zone definitions (VTIMEZONE) generated so other apps read times correctly
- Podcast tab (PODCAST_URL) alongside Podcast Admin

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.env.example

@@ -10,3 +10,4 @@ AUDIOBOOKS_URL=https://audiobooks.necloud.us
 # First-time passkey enrolment. If unset, a random code is printed in the server log while no passkey exists.
 HUB_SETUP_CODE=
 VERSE_URL=https://versebyversewithnate.us/admin
+PODCAST_URL=http://172.16.16.106:8383/