UI: refresh dashboard design system

[mousberg]

Summary

• Swap Inter for Space Grotesk typography (geometric, techy feel)
• Punchier accent colors with teal secondary
• Better hover states, shadows, and micro-interactions
• More breathing room in layout

Changes

• ui/src/styles/base.css - typography, colors, animations
• ui/src/styles/components.css - cards, buttons, stats, callouts
• ui/src/styles/layout.css - navigation, spacing, page titles

Test plan

• Run pnpm dev in /ui and verify dashboard renders
• Check both light and dark themes
• Test responsive behavior on mobile sizes
• Verify all views (Overview, Chat, Config, Channels, etc.)

[steipete]

Landed via temp rebase onto main.

• Gate: pnpm lint && pnpm build && pnpm test
• Land commit: 48ca19c
• Merge commit: 2fcbed2

Thanks @mousberg!

[bradleypriest]

@mousberg there's some specificity issues with the light theme.
Try visiting <your-web-ui-url>/chat, and toggling on the thinking mode in light and dark modes.

In light mode,

:root[data-theme="light"] .btn--icon {
  background: #fff;
  border-color: var(--border);
  box-shadow: 0 1px 2px #1018280d;
  color: var(--muted);
}

is overriding

.btn.active {
  border-color: var(--accent);
  background: var(--accent-subtle);
  color: var(--accent);
}

[mousberg]

Thanks @bradleypriest! Fixed the light mode specificity issue in #1816 - added :root[data-theme="light"] .btn--icon.active override.