ci: retry registry login

.gitea/workflows/container.yml

@@ -61,7 +61,17 @@ jobs:
             echo "REGISTRY_TOKEN is not configured; image will build but publishing is skipped."
             exit 0
           fi
-          echo "${REGISTRY_TOKEN}" | docker login git.wimby.cz --username wimby --password-stdin
+          for attempt in 1 2 3; do
+            if echo "${REGISTRY_TOKEN}" | docker login git.wimby.cz --username wimby --password-stdin; then
+              break
+            fi
+            if [ "${attempt}" -eq 3 ]; then
+              echo "Registry login failed after ${attempt} attempts."
+              exit 1
+            fi
+            echo "Registry login failed (attempt ${attempt}); retrying..."
+            sleep $((attempt * 5))
+          done
 
       - name: Build image
         shell: bash