CI: change registry user, rename step

.gitea/workflows/rebuild.yml

@@ -18,11 +18,11 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v2
 
-      - name: Login to Docker Hub
+      - name: Login to Gitea container registry
         uses: docker/login-action@v2
         with:
           registry: git.kucharczyk.xyz
-          username: ${{ gitea.repository_owner }}
+          username: lukas
           password: ${{ secrets.GITEA_TOKEN}}
 
       - name: Build and Push Docker Image