This PR removes all CMS code from the `www` app. This includes fetching
of blog posts, API routes for proxying blog posts and types.
All functionality should remain the same (and the number of blog posts
should be the same).
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Chores**
* Removed CMS integration, APIs, preview/draft/revalidate endpoints,
related env vars and dependency; switched to static markdown-only blog
pipeline.
* **Refactor**
* Simplified image and author resolution, tightened component props to
static post shapes, and migrated imports to path aliases.
* **Documentation**
* Deleted CMS integration docs and rich-text conversion helpers.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Ivan Vasilov