NE Hub: Seafile, OnlyOffice, Plex, calendar and mail in one PWA

- Mobile-first PWA (phone tab bar with More menu, iPad/desktop rail)
- Passkey (WebAuthn) sign-in gates the whole app; first passkey via setup code
- Files: Seafile browse/upload/new doc/rename/move/share link/preview/delete
- In-app OnlyOffice editing with JWT-signed configs and save-back to Seafile
- Plex music player via plex.tv sign-in and a server-side proxy
- Calendar agenda from private ICS links (recurrence + time zones)
- Search, Home dashboard, webmail deep links, audiobooks frame
- Dockerfile, compose, and a Gitea Actions workflow that builds the image

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

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