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/services/index.ts

@@ -1,5 +1,6 @@
 // Service exports
 export { apiClient } from './api';
 export { reportService } from './reportService';
+export { analyticsService } from './analyticsService';
 export type { ApiError } from './api';
 export type { CreateReportPayload, UploadPhotoResponse } from './reportService';