feat(#375): frontend token usage and cost dashboard

- Install recharts for data visualization
- Add Usage nav item to sidebar navigation
- Create telemetry API service with data fetching functions
- Build dashboard page with summary cards, charts, and time range selector
- Token usage line chart, cost breakdown bar chart, task outcome pie chart
- Loading and empty states handled
- Responsive layout with PDA-friendly design
- Add unit tests (14 tests passing)

Refs #375

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/lib/api/index.ts

@@ -12,3 +12,4 @@ export * from "./knowledge";
 export * from "./domains";
 export * from "./teams";
 export * from "./personalities";
+export * from "./telemetry";