CI: export REGISTRY secret into step env

.gitea/workflows/publish.yml

@@ -11,6 +11,8 @@ jobs:
       - uses: actions/checkout@v4
 
       - name: Build and push image
+        env:
+          REGISTRY: ${{ secrets.REGISTRY }}
         run: |
           set -e
           IMAGE=git.obahan.xyz/hermes/wiki-jokes