Enhance Docker build workflow with registry token validation

- Added a check in docker-build.yml to ensure the REGISTRY_TOKEN is set before attempting to log in to the Gitea Container Registry.
- Included an error message to guide users in adding the necessary secret for successful authentication.

.gitea/workflows/docker-build.yml

@@ -28,8 +28,13 @@ jobs:
         run: |
           echo "host=${GITHUB_SERVER_URL#https://}" >> $GITHUB_OUTPUT
 
+      # REGISTRY_TOKEN: Personal Access Token с правом write:package (или токен из Package Registry)
       - name: Log in to Gitea Container Registry
         run: |
+          if [ -z "${{ secrets.REGISTRY_TOKEN }}" ]; then
+            echo "::error::REGISTRY_TOKEN не задан. Добавьте секрет с токеном (scope: write:package)."
+            exit 1
+          fi
           echo "${{ secrets.REGISTRY_TOKEN }}" | docker login ${{ steps.registry.outputs.host }} -u ${{ github.actor }} --password-stdin
 
       - name: Build and push