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>

public/manifest.webmanifest

@@ -0,0 +1,11 @@
+{
+  "name": "NE Hub",
+  "short_name": "NE Hub",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#0f1115",
+  "theme_color": "#0f1115",
+  "icons": [
+    { "src": "/icon.svg", "sizes": "any", "type": "image/svg+xml", "purpose": "any maskable" }
+  ]
+}