ci: push image to fritzlab-public org

This repo was transferred from fritzlab to fritzlab-public so the container
package's anonymous-pull access (governed by org visibility in Gitea 1.26.1)
remains open after the rest of fritzlab/* flips to limited.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/main.yaml

@@ -10,7 +10,7 @@ jobs:
 
       - uses: https://code.fritzlab.net/action/image-build@v1
         with:
-          image: code.fritzlab.net/fritzlab/flock
+          image: code.fritzlab.net/fritzlab-public/flock
           build-args: GIT_SHA=${{ github.sha }}
           smoke-test: |
             docker run --rm $IMAGE --help || true
@@ -18,7 +18,7 @@ jobs:
 
       - uses: https://code.fritzlab.net/action/image-push@v1
         with:
-          image: code.fritzlab.net/fritzlab/flock
+          image: code.fritzlab.net/fritzlab-public/flock
           token: ${{ secrets.CI_BOT_TOKEN }}
-          org: fritzlab
+          org: fritzlab-public
           name: flock