fix empty tag and enable debug on docker-buld.yml

.gitea/workflows/docker-build.yml

@@ -14,7 +14,10 @@ jobs:
 
       - name: Extract short SHA
         id: vars
-        run: echo "SHORT_SHA=$(echo $GITEA_SHA | cut -c1-7)" >> $GITEA_OUTPUT
+        run: echo "SHORT_SHA=$(git rev-parse --short HEAD)" >> $GITEA_OUTPUT
+
+      - name: Debug SHA
+        run: echo "Tag: ${{ steps.vars.outputs.SHORT_SHA }}"
 
       - name: Set up Docker Buildx
         run: |