feat: build StatusBadge component

## Task
Create `src/components/StatusBadge.tsx` for transaction status display.

## Props
```ts
interface StatusBadgeProps {
  status: 'pending' | 'success' | 'failed';
}
```

## Styling
- pending → yellow badge
- success → green badge
- failed → red badge

## Acceptance Criteria
- [ ] Correct color per status
- [ ] Renders status text