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