Implement sitemap generation functionality with a new API endpoint at `/api/v1/sitemap`. The sitemap includes all published pages (excluding error pages) with proper URL formatting, last modified dates, and XML escaping. This improves SEO by providing search engines with an up-to-date sitemap.

- Add sitemap.xml rewrite rule in Next.js config
- Create sitemap API endpoint handler
- Implement sitemap generation utilities including URL normalization and deduplication
- Export getSitemapXml function from data layer

…dpoint

- Validate that only GET requests are allowed, returning 405 for other methods
- Add Cache-Control headers to improve performance and reduce server load
- Wrap sitemap generation in try-catch to handle errors gracefully
- Remove unnecessary escapeXml call for lastmod dates and simplify dedupe logic
- Make getSitemapEntries function private to module

Change getSitemapXml from named to default export for consistent import patterns
Add Sentry error capture to sitemap API endpoint for improved monitoring

- Replace dynamic pathname generation with stored `pathname` field from CMS
- Filter pages by `_status: "published"` instead of just excluding error pages
- Remove XML escaping as URLs are already validated and safe
- Add Sentry warning for pages missing pathname to aid debugging
- Simplify code by removing deduplication and custom escape functions

The sitemap was previously served via an API route with a rewrite. This change replaces it with a static page (`sitemap.xml.page.js`) to improve performance and caching. The new page uses `getServerSideProps` to generate the XML with proper cache headers and error handling via Sentry.