fix: upgrade Node.js version in release workflow to meet semantic-release requirements

- Update release workflow from Node.js 18 to Node.js 20
- This resolves the semantic-release error: "node version >=20.8.1 is required"
- CI workflow already tests both Node.js 18 and 20 for compatibility
- package.json engines field supports ">=18" so this change is backward compatible

The release workflow will now use Node.js 20 which meets semantic-release
requirements while maintaining compatibility with the existing codebase.

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

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

Author: cristotodev

.github/workflows/release.yml

@@ -24,7 +24,7 @@ jobs:
       - name: Setup Node.js
         uses: actions/setup-node@v4
         with:
-          node-version: '18'
+          node-version: '20'
           cache: 'npm'
 
       - name: Install dependencies