Use GitHub-hosted mirror for gitea-release-action

The Gitea runner cannot reach gitea.com (IPv6 timeout), so switch to
the akkuman/gitea-release-action mirror hosted on GitHub.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitea/workflows/ci.yaml

@@ -129,7 +129,7 @@ jobs:
           echo "Container image: \`${IMAGE}:${{ steps.semver.outputs.full }}\`" >> RELEASE_NOTES.md
 
       - name: Create Gitea release
-        uses: https://gitea.com/actions/gitea-release-action@v1
+        uses: akkuman/gitea-release-action@v1
         with:
           tag_name: ${{ github.ref_name }}
           name: v${{ steps.semver.outputs.full }}