Add feature highlights and footer to the landing page #120

Part of #84.

The landing page at /landing currently has the hero and the portal screenshot only (landed in #119). The page ends abruptly after the screenshot.

This slice adds the two sections named as follow-ups in #119:

• a feature highlights section below the screenshot with four cards covering the surfaces the hero promises: software templates, the catalog, GitHub integration and the answer engine, each linking to its live surface (/self-service, /catalog, /showcase, /search)
• a footer that repeats the path into the demo (showcase and catalog links plus the guest note) so the page has a clear end and a second chance to enter the demo

Acceptance:

• highlights render with one card per surface and working router links
• footer renders with demo links
• component tests cover both sections
• mise run lint and mise run test pass
• screenshot of /landing showing the new sections

The route placement question (whether /landing replaces /) stays with Johnny and is out of scope here.