Tasks tab: NE Hub lists plus iCloud reminder lists where Apple exposes them

- Lists, quick add, due dates, notes, complete/reopen, delete; Home card for overdue/due today
- iCloud VTODO lists read and written over CalDAV (If-Match, edits patch the latest copy so
  priority/alarms survive); NE Hub lists work regardless
- Fix: text inside a nested VALARM was read as the task's / event's own description and then
  written back on edit; nested components are now skipped (regression tests added)

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

README.md

@@ -31,6 +31,9 @@ e.g. hub.necloud.us. Settings: `SEAFILE_URL`, `ONLYOFFICE_URL` env vars in docke
   - **iCloud (two-way)**: connect with an Apple ID and an *app-specific password* (appleid.apple.com). Credentials are
     encrypted in `/data/icloud.json`; only `*.icloud.com` is contacted. Edits keep alarms and attendees intact.
   - **ICS links** (Google secret address, Outlook/M365 published calendar) are read-only.
+- **Tasks**: to-do lists stored in NE Hub (`/data/tasks.json`), with due dates, notes and completion. If the connected iCloud
+  account exposes reminder lists over CalDAV they appear too and sync both ways. Apple hides Reminders lists that were upgraded
+  for iOS 13+, so for most accounts only NE Hub lists are available.
 - **Search**: libraries, file names (scans libraries if Seafile has no search index) and Plex artists/albums/tracks.
 - **Music**: Plex player. Sign in goes through plex.tv (no password handled), the server proxies your Plex server and adds the token itself, and a mini player keeps playing as you move between tabs; the queue (play next / add to queue) and position are remembered.
 - **Audio**: embeds audiobooks.necloud.us; sign-in details saved in Settings can be copied with one tap.