chore(deps): remove chart.js and render the results panel chart with uPlot

[xe-nvdk]

Context

chart.js is a dependency with exactly one use: src/lib/components/ResultsPanel.svelte:3. Everything else charts with uplot, which is smaller and faster. Carrying two charting libraries means two rendering models, two theming paths, and two bundle costs.

Small, self-contained cleanup. Part of #19.

Scope

• Port the chart in ResultsPanel.svelte (line and bar) to uPlot
• Remove chart.js from package.json and the lockfile
• Confirm no other import survives: grep -rn "chart.js\|from 'chart" src/
• Keep theme awareness — the chart must restyle on light/dark switch

Where to look

• src/lib/components/MetricChart.svelte is the smallest existing uPlot wrapper; copy its options shape
• src/lib/components/logs/LogHistogram.svelte shows uPlot bars
• Theme detection today is document.documentElement.classList.contains('dark')

Notes

Best picked up after the units and colors modules land, so the port uses the shared formatter and palette instead of inventing a third one. It can be done before them, but then expect a follow-up.

Acceptance criteria

• The results-panel chart renders line and bar the same as before
• chart.js is gone from package.json, the lockfile, and node_modules
• The production bundle is measurably smaller
• npm run check and npm run build both pass

[xe-nvdk]

Closing: the dashboards feature has been dropped from Launchpad. The implemented work was removed in #87 and this work will not be picked up. Recoverable from git tag pre-dashboards-removal-backup if the feature is ever revived.