Add a human-facing web interface at /ui/ for browsing IPS package
repositories. Uses Askama templates, HTMX for interactivity, and
Pico.css for styling.
Routes:
- /ui/ - Publisher list with package counts
- /ui/packages/:publisher - Paginated package list
- /ui/search - Search with HTMX search-as-you-type
- /ui/package/:publisher/*fmri - Package detail with lazy manifest
- /ui/p5i - P5I file generation for installing package sets
