(doc) Update README and clean up workflow step name

Updated README to document registry authentication setup using REGISTRY_USERNAME and REGISTRY_TOKEN configured in repo settings. Also removed debug info from workflow step name.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.gitea/workflows/build.yml

@@ -28,7 +28,7 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
-      - name: Login to Registry using user=${{ gitea.actor }}/pass=${{ gitea.token }}
+      - name: Login to Registry
         # Gitea automatically provides these secrets:
         # - `REGISTRY_USERNAME` - defined as action variable in repo settings
         # - `REGISTRY_TOKEN` - defined as action secret in repo settings, created in user settings as personal access token with `write:packages` scope

README.md

@@ -51,6 +51,15 @@ The project includes a Gitea Actions workflow that automatically:
 
 The workflow is defined in [.gitea/workflows/build.yml](.gitea/workflows/build.yml)
 
+### Registry Authentication
+
+The workflow authenticates to the Docker registry using credentials configured in the repository settings:
+
+1. **REGISTRY_USERNAME** - Action variable defined in repository settings (Settings → Actions → Variables)
+2. **REGISTRY_TOKEN** - Action secret defined in repository settings (Settings → Actions → Secrets)
+
+The `REGISTRY_TOKEN` should be a personal access token created in your Gitea user settings with the `write:packages` scope.
+
 ### Image Naming
 
 Images are pushed with two tags: