fix: remove stale local-registry container before starting new one

.gitea/workflows/docker.yml

@@ -52,7 +52,9 @@ jobs:
       # without hitting Gitea's broken Bearer token endpoint. regctl then
       # copies from localhost:5000 to Gitea using basic auth.
       - name: Start local registry
-        run: docker run -d -p 5000:5000 --name local-registry registry:2
+        run: |
+          docker rm -f local-registry 2>/dev/null || true
+          docker run -d -p 5000:5000 --name local-registry registry:2
 
       - name: Build standard image
         uses: docker/build-push-action@v6