fix(docs): standardize card wrapper across all docs pages

The docs pages were a 50/50 split: pages I added recently (customization,
deployment, getting-started, integrations, layout-blueprint, migration,
recipes, rtl, plugins-overview) used the standard
<div class="row"><div class="col-12"><div class="card"><div class="card-body">
wrapper, but the older docs pages (introduction, layout, color-mode,
browser-support, license, how-to-contribute, components/*, all
javascript/*) rendered their MDX directly inside .container-fluid with
no wrapper.

Two visible consequences:
- Half the pages had a white card background; the other half showed the
  body-tertiary backdrop through (no visual container at all)
- Half the pages had my .docs-page typography (h5 separators, styled
  tables, info callouts, pill inline code) and the other half didn't,
  because the prose styles are scoped under .card > .card-body

Wraps the MDX content (or hand-written content in color-mode.astro and
layout.astro) in the same row/col-12/card/card-body markup so every
docs page now renders against an identical white card with consistent
prose typography, table styling, code-block treatment, and callout
spacing.

FAQ keeps its custom design (it intentionally breaks the card pattern
to deliver a hero + chips + accordion layout).

13 pages mechanically wrapped via a Python regex over the
<Component /> placeholder + indent capture; layout.astro and
color-mode.astro hand-edited because they had additional non-MDX
content (a tips callout and a navbar demo respectively).