feat(web): local React/Recharts dashboard (codeburn web)

[iamtoruk]

What

Adds a local web dashboard served by codeburn web: a Vite + React 19 + Tailwind v4 + Recharts SPA (dash/) plus a small local server that serves the built UI and a /api/usage endpoint backed by the existing menubar aggregation. Everything is computed and served on the local machine. No account, nothing uploaded.

UI

• Midnight theme with CodeBurn's orange chart ramp.
• Hero total cost, a stacked-by-model daily bar chart with a custom tooltip and hover-dim, metric cards (cost / tokens / calls / sessions / cache hit / one-shot), by-tool and by-activity bar lists, and top-projects and tools tables.
• Period tabs (today / week / 30 days / month / all) and a provider filter.
• react-query with skeleton loading states.

How it is wired

• dash/ is a standalone Vite app. npm run build:dash builds it into dist/dash, which ships via the package files and is served at runtime. A missing build falls back to a help message.
• codeburn web [--period --provider --from --to --port --no-open] starts the server (default port 4747, falls back to a free port if taken) and opens the browser. Static assets come from dist/dash; /api/usage re-aggregates per request via buildMenubarPayloadForRange.
• The static handler is path-traversal guarded; the CLI is EPIPE-safe.

Verify

npm run build:dash     # build the SPA (also the last step of npm run build)
npm run dev -- web     # serve and open the browser

Checked locally: serves the SPA shell and assets (200) and /api/usage returns live data for the current month (cost, calls, 8 tools, 38 daily entries each with per-model breakdown for the chart). Full suite 1239 green, main project tsc clean.

Notes

• The JS bundle is ~625 kB (Recharts). Fine for a local-only dashboard; can be code-split later.
• npm run build now runs build:dash as its final step (installs dash deps + Vite build).