style(docs): add reading-friendly typography for .docs-page

Adds a body class `.docs-page` to every documentation page and styles
its card-body for prose:

- More generous padding (1.5rem / 2rem on md+)
- Headings get vertical rhythm appropriate for long-form reading
  (margin-top: 1.75em, scaled font sizes per level)
- Paragraphs, lists, blockquotes, tables: 1.6 line-height + 1rem
  bottom margin
- Inline code gets a subtle pill background
- Block code preserves overflow-x and consistent spacing
- Reference tables get a hairline border + tertiary background on
  header cells
- Blockquotes render as info callouts (left border + subtle bg)
- Prose links get underline + offset for clearer affordance

Demo pages are unaffected -- everything is scoped under .docs-page.

Adds the partial to adminlte.scss imports.

Includes the docs-page class addition on all 25 docs page wrappers
(under src/html/pages/docs/).