Fix cosmetic UI issues: link colors, dark/light toggle, mobile, API docs
- ASN links now inherit surrounding text color instead of the accent purple, so they read correctly inside badges/notices in dark mode instead of clashing with success/warning/danger colors.
- Add a dark/light mode toggle button, persisted to localStorage, with an inline pre-paint script to avoid a flash of the wrong theme.
- Widen mobile breakpoints (topbar/shell padding, card padding, input font-size) so the page is comfortable down to ~360px.
- Add the missing second JSON API example (per-peer authorization check) next to the existing single-ASN example.
- Footer now shows how long ago the Routinator snapshot was generated ("(N minutes ago)"), fetched unconditionally so it's available even on the empty landing page.
Co-Authored-By: Claude Sonnet 5 noreply@anthropic.com Claude-Session: https://claude.ai/code/session_01SdWQ3jVyzwRoQjVfAfK4mZ