fix(ui): a11y, theming, states, dataviz and perf overhaul

[ErickJ3]

• self-host Geist Mono via @font-face and fix theme FOUC with a pre-paint script
• restore green dark --primary and add contrast-checked severity/status oklch tokens
• replace raw Tailwind palette and ad-hoc muted text with semantic tokens
• add app-level error boundary and keyboard-accessible trace rows
• label all filter inputs, selects and pagination controls
• add focus-visible rings, toast aria-live, chart role=img summaries and skip-to-content link
• fix heading hierarchy and add metric trend text
• add friendly error copy, contextual error titles and per-route skeletons
• surface the correlated-logs failure and make the 100-item counts honest
• move hand-rolled buttons to the Button primitive and style the settings checkbox
• fix the hsl(oklch()) bar-color bug and the zero-value tooltip guard
• add chart axis scale and a stacked-bar legend
• scope auto-refresh invalidation to the active route only
• memoize chart transforms, clamp refreshInterval and simplify command-palette keys
• align card and badge radii to the radius-0 system