feat(web): marketing Home page and the product component library (ADR 0023)

Product UI components are built once at design size from the Figma file and reused by the marketing mockups and, later, the app. Text contrast tokens now meet WCAG AA in both themes, with a test. Pricing stays hidden until decided.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014SdXCbrN5PtGExkpvMaMHx

web/public/icons/globe.svg

@@ -0,0 +1,6 @@
+<svg preserveAspectRatio="none" overflow="visible" style="display: block;" width="18" height="18" viewBox="0 0 18 18" fill="none" xmlns="http://www.w3.org/2000/svg">
+<g id="Icon">
+<path id="Vector" d="M9 16.5C13.1421 16.5 16.5 13.1421 16.5 9C16.5 4.85786 13.1421 1.5 9 1.5C4.85786 1.5 1.5 4.85786 1.5 9C1.5 13.1421 4.85786 16.5 9 16.5Z" stroke="#6B675E" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round"/>
+<path id="Vector_2" d="M1.5 9H16.5M9 1.5C10.876 3.55376 11.9421 6.21903 12 9C11.9421 11.781 10.876 14.4462 9 16.5C7.12404 14.4462 6.05794 11.781 6 9C6.05794 6.21903 7.12404 3.55376 9 1.5Z" stroke="#6B675E" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round"/>
+</g>
+</svg>