Remove the micro posts feature from the codebase including:
- Backend: API routes, handlers, and database models (MicroPost, MicroPostLike)
- Frontend: React components (Heatmap, MicroComposer, MicroList, MicroPage)
- Pages: micro.astro page and navigation links
- Documentation: API docs and user guide sections
This simplifies the application by removing a feature that is no longer needed.
BREAKING CHANGE: All micro posts related API endpoints (/api/micros) are removed.
Existing micro posts data will not be accessible after this change.
