fix(docs): align docs spacing with notion

[luandro]

Summary

• scope tighter typography spacing to .theme-doc-markdown so docs match Notion layout
• reduce paragraph, list, and list item margins while leaving marketing pages untouched

Testing

• bunx prettier --write src/css/custom.css

Resolves #48.

[luandro]

Update

• Scoped tighter paragraph/list spacing to .theme-doc-markdown so docs pages better mirror Notion authoring.
• Reduced block/list margins without touching marketing pages.

Testing

1. bun run dev
2. Visit http://localhost:3000/docs/uninstalling-comapeo (or any docs page).
3. Compare paragraph and list spacing against Notion reference; spacing should now match closely without extra gaps.

Local reference screenshots: screenshots/review-spacing-before.png and screenshots/review-spacing-after.png.