fix(ci): Forgejo Actions auth + kustomize cleanup in validate-k8s workflow

.forgejo/workflows/argocd-sync.yaml

@@ -12,7 +12,13 @@ jobs:
     runs-on: docker
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        run: |
+          REPO_URL="${{ gitea.server_url }}/${{ gitea.repository }}.git"
+          CLONE_URL="https://${{ secrets.CI_RUNNER }}:${{ secrets.CI_RUNNER_SECRET }}@${REPO_URL#https://}"
+          git clone --depth 1 "$CLONE_URL" .
+          cd ${GITHUB_WORKSPACE}
+          git fetch origin main
+          git checkout main
 
       - name: Install ArgoCD CLI
         run: |