Fix CI: replace checkout action with manual git clone

The runner cannot resolve the internal 'forgejo' hostname used by
actions/checkout@v4. Use direct git clone with public URL instead.

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

.forgejo/workflows/deploy.yml

@@ -13,7 +13,8 @@ jobs:
     runs-on: docker
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        run: |
+          git clone --depth 1 --branch main https://forge.studio-variable.com/${{ github.repository }}.git .
 
       - name: Setup SSH
         run: |