nx-webmail: switch Umbrel app to prebuilt GHCR image

nx-webmail/README.md

@@ -18,6 +18,17 @@
 3. Open:
    http://localhost:3001
 
+## Publish image for Umbrel
+
+Umbrel installation is most reliable when your app uses a prebuilt image from a registry.
+
+1. Recommended: use the GitHub Action `.github/workflows/publish-nx-webmail-image.yml`.
+2. The workflow reads `version` from `nx-webmail/umbrel-app.yml` and publishes:
+   - `ghcr.io/weektab/nx-webmail:<version>`
+   - `ghcr.io/weektab/nx-webmail:latest`
+3. Manual fallback:
+   docker buildx build --platform linux/amd64,linux/arm64 -t ghcr.io/weektab/nx-webmail:1.0.1 --push .
+
 ## Umbrel app packaging
 
 This repository is prepared for Umbrel app-store usage.
@@ -41,6 +52,7 @@ This repository is prepared for Umbrel app-store usage.
 Notes:
 - Umbrel uses the `app_proxy` service in `docker-compose.yml`.
 - Internal app port is `3001`.
+- `server` uses a prebuilt registry image (`ghcr.io/weektab/nx-webmail:1.0.1`).
 - If your store prefix changes, update `id` in `umbrel-app.yml` and `APP_HOST` in `docker-compose.yml`.
 
 ## Notes