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>

docker-compose.yml

@@ -16,6 +16,7 @@ services:
       ONLYOFFICE_URL: ${ONLYOFFICE_URL:-https://onlyoffice.necloud.us}
       AUDIOBOOKS_URL: ${AUDIOBOOKS_URL:-https://audiobooks.necloud.us}
       VERSE_URL: ${VERSE_URL:-https://versebyversewithnate.us/admin}
+      PODCAST_URL: ${PODCAST_URL:-http://172.16.16.106:8383/}
       ONLYOFFICE_JWT_SECRET: ${ONLYOFFICE_JWT_SECRET:-}    # same value as the OnlyOffice server's JWT secret
       PUBLIC_URL: ${PUBLIC_URL:-}                           # e.g. https://hub.necloud.us (OnlyOffice posts saved edits here)
       HUB_SETUP_CODE: ${HUB_SETUP_CODE:-}                   # first passkey; if empty, a code is printed in the log