Fix Node.js version for GitHub Actions build

Update from Node.js 18 to 20 to resolve undici File compatibility issue

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: PwnTips

.github/workflows/deploy.yml

@@ -25,7 +25,7 @@ jobs:
       - name: Setup Node
         uses: actions/setup-node@v4
         with:
-          node-version: 18
+          node-version: 20
           cache: npm
       - name: Setup Pages
         uses: actions/configure-pages@v4