- Move shared structural styles to frontend/src/assets/pagerite.css
with conservative variables, and purple theme overrides to
frontend/src/assets/themes/purple/theme.css.
- Backend now links the base and theme stylesheets as separate files
so they can be swapped or augmented.
- Add blocking="render" to stylesheet links to avoid FOUC.
- Drop redundant defer from module script tags.
- Update related docs and comments.