- ChartContainer: replace stroke-border/fill-muted (ShadCN tokens we
don't have) with var(--chart-grid) so recharts CSS overrides actually work
- Dashboard chart: remove YAxis (ShadCN interactive bar has none)
- Remove unused formatAxisValue, formatAxisDuration, tick calculations
- Exact ShadCN structure: CartesianGrid vertical={false}, XAxis with
tickMargin/minTickGap, single Bar with fill var(--color-{metric})
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>