Documented distributing the Docker image through the Gitea registry.

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

deploy/README.md

@@ -21,7 +21,7 @@ The two settings are independent. [Setup with nginx and PostgreSQL on the host](
 ## Requirements
 
 - Docker 20.10 or newer, `bash` and `openssl` on the host. The Compose plugin is needed only when Traefik or PostgreSQL run as containers of this stack.
-- The application image on the host: `docker build -t rezervator:latest .` in the repository root, or pulled from a registry. The image must match the CPU architecture of the host.
+- The application image on the host: `docker build -t rezervator:latest .` in the repository root, or pulled from a registry (see [Distributing the image](#distributing-the-image)). The image must match the CPU architecture of the host.
 - A DNS record for every customer domain pointing to the host
 
 ## First setup
@@ -37,6 +37,47 @@ With `REZERVATOR_PROXY=traefik`, `REZERVATOR_TLS=true` gets a Let's Encrypt cert
 
 The session cookie is marked `Secure`. Whatever the setup, customers must reach the application over HTTPS, otherwise logging in works only on `localhost` addresses.
 
+## Distributing the image
+
+Building the image takes several minutes and needs the Rust toolchain image. To set up another server quickly, build once, push the image to a container registry and pull it elsewhere. Gitea has a registry built in; the examples use the one at `gitea.itsolved.cz` and the organization `itsolved`.
+
+On the server where the image was built:
+
+```sh
+docker login gitea.itsolved.cz
+docker tag rezervator:latest gitea.itsolved.cz/itsolved/rezervator:1.2.0
+docker push gitea.itsolved.cz/itsolved/rezervator:1.2.0
+```
+
+Log in with a Gitea user name and an access token (Settings → Applications) that may write packages. Use the version from `Cargo.toml` as the tag rather than only `latest`: it shows what runs where, and an older version stays available.
+
+On another server:
+
+```sh
+docker login gitea.itsolved.cz      # only when the package is not public; a token that may read packages is enough
+docker pull gitea.itsolved.cz/itsolved/rezervator:1.2.0
+```
+
+and in `.env`:
+
+```ini
+REZERVATOR_IMAGE=gitea.itsolved.cz/itsolved/rezervator:1.2.0
+```
+
+To release a new version, build and push it under a new tag, then on every server pull it, change the tag in `.env` and run `./rezervator.sh upgrade --all`.
+
+Things to know:
+
+- The image runs only on the CPU architecture it was built on (`x86_64` when built on such a server).
+- The package belongs to the organization and follows its visibility: the image of a public organization can be pulled without logging in. The image contains no configuration or passwords.
+- If the push fails with `413 Request Entity Too Large`, the reverse proxy in front of Gitea limits the upload size; raise `client_max_body_size` in its nginx server block.
+
+Without a registry, an image can be copied to one server directly:
+
+```sh
+docker save rezervator:latest | gzip | ssh user@other-server 'gunzip | docker load'
+```
+
 ## Setup with nginx and PostgreSQL on the host
 
 ```ini