fix: replace actions/checkout with git clone (no Node.js required)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/build-release.yml

@@ -9,7 +9,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        run: |
+          git clone --depth 1 --branch "${GITHUB_REF_NAME}" \
+            "${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}.git" .
 
       - name: Validate environment
         run: |