Holdings UI overhaul, CSS design system

Cleaned up of the holdings page and start reviewing design system:

• Full-width layout shows more details on big screens. Compact navigation to save space.
• Better contrast colors in light and dark mode.
• Fixed tag filter on iOS tap and hover colors.
• Various tweaks: tag list gaps, badge positioning, table heading color variable.
• Table rows navigate on click instead of inline links.

Nerdy details

• Modular css components for ergonomics, cacheability and: tags.css, badges.css, inputs.css, colors.css.
• Parameterize colors into CSS variables; use oklch color space.
• Icon system: --icon-size, icon-wrapper, responsive sizing, new filter.svg.
• Make spacing consistent.
• bin/diet utility for finding large files.
• Updated ruby-prof ~> 2.x to fix broken builds on Fedora 43.