feat: enhance release notes with collapsible changelog sections

- Add collapsible functionality to release notes with Show/Hide Details buttons
- Display version titles in table of contents for better navigation
- Default expand first 2 releases, collapse others to improve page load performance
- Fetch releases from GitHub API with fallback to repo.databend.com
- Support both stable and pre-release versions (including nightly builds)
- Fix markdown link escaping to prevent broken links
- Escape < and > characters to avoid MDX compilation errors

Author: BohuTANG