style(ui): unify sidebar badges to primary, improve card depth and affordance
Phase 1 audit (P0 & P1):
- Sidebar: badges use primary (teal) instead of secondary (magenta)
- AdminDashboardStatCard: 0% trend shown as muted, never red
- AdminDashboardTrafficCard: remove fake Math.random() data, show empty state
- Dark theme: increase card luminance (0.21), stronger borders
- Card variants: add border-white/10 to glass, border-border to default
- Header: search input bg-card + border-white/10, migrate kodo-* to semantic tokens
- MiniPlayer: h-20 max (was h-24)
Co-authored-by: Cursor <cursoragent@cursor.com>
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