feat: implement analytics dashboard layout (task 10)

- Add analytics types (AnalyticsSummary, DateRange)
- Create analyticsService for API calls and CSV export
- Implement DateRangeSelector component with presets
- Create StatCard component for summary statistics
- Build responsive AnalyticsPage with:
  - Summary statistics cards (reports, events, users, litter collected)
  - Date range filtering with presets
  - CSV export functionality
  - Loading and error states
  - Responsive grid layout

Requirements: 5.1, 5.5

src/components/analytics/index.ts

@@ -0,0 +1,2 @@
+export { DateRangeSelector } from './DateRangeSelector';
+export { StatCard } from './StatCard';