[FE-013] usePerformanceMetrics swallows fetch errors silently (no error state)

The catch block in usePerformanceMetrics sets data to empty array without setting an error state — consumers cannot distinguish empty data from a fetch failure.

**Evidence:**
```
web/dashboard/hooks/useTradeData.ts catch block sets setData([]) with no error propagation
```

**File:** web/dashboard/hooks/useTradeData.ts:~1
**Agent:** FE-013