Roundcube as its own image built by the workflow (no config file or newer Compose needed)

- roundcube/: official Roundcube plus hub.php settings
- workflow builds and pushes git.necloud.us/nate/hub-roundcube, and runs the player and webmail tests
- compose uses the image instead of an inline config

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

README.md

@@ -69,8 +69,8 @@ e.g. hub.necloud.us. Settings: `SEAFILE_URL`, `ONLYOFFICE_URL` env vars in docke
   authenticated SMTP must be allowed for the mailbox. Then put `M365_CLIENT_ID`, `M365_CLIENT_SECRET`, `M365_TENANT` (the tenant ID) and `PUBLIC_URL`
   (your hub address, used for the redirect) in `.env` and `docker compose up -d`. The Roundcube login then shows **Login with Microsoft 365**. Microsoft's sign-in
   page cannot be shown inside a frame, so that one step opens in the whole window and returns you to the Mail tab. Personal Outlook.com accounts are not covered.
-  Roundcube's data (settings, address book, its encryption key) is in the `nehub-roundcube` volume. To change the presets, edit the `roundcube_hub` config in
-  `docker-compose.yml` (needs Docker Compose 2.23.1 or newer). To use a webmail you run elsewhere instead, set `WEBMAIL_URL` (it must allow being framed:
+  Roundcube's data (settings, address book, its encryption key) is in the `nehub-roundcube` volume. The webmail is its own image (`git.necloud.us/nate/hub-roundcube`, built by the Gitea workflow from `roundcube/`: the official Roundcube plus
+  `roundcube/hub.php`), so any compose tool can run it. To change the presets, edit `roundcube/hub.php`. To use a webmail you run elsewhere instead, set `WEBMAIL_URL` (it must allow being framed:
   no `X-Frame-Options`, and `Content-Security-Policy: frame-ancestors https://<your hub address>`). With neither, Mail is just the shortcut cards.
 
       roundcube: