ci: use base64 encoded SSH key

.gitea/workflows/deploy.yml

@@ -27,7 +27,7 @@ jobs:
       - name: Setup SSH key
         run: |
           mkdir -p ~/.ssh
-          printf '%s' "${{ secrets.NAS_SSH_KEY }}" > ~/.ssh/nas_key
+          echo "${{ secrets.NAS_SSH_KEY_B64 }}" | base64 -d > ~/.ssh/nas_key
           chmod 600 ~/.ssh/nas_key
           ssh-keyscan -p 22 ${{ secrets.NAS_HOST }} >> ~/.ssh/known_hosts 2>/dev/null