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/types/index.ts

@@ -119,3 +119,21 @@ export interface FilterState {
   quantities?: QuantityLevel[];
   verificationStatus?: VerificationStatus[];
 }
+
+// Analytics types
+export interface AnalyticsSummary {
+  totalReports: number;
+  totalEvents: number;
+  totalUsers: number;
+  totalLitterCollected?: number; // in kilograms
+  periodComparison?: {
+    reports: number; // percentage change
+    events: number;
+    users: number;
+  };
+}
+
+export interface DateRange {
+  start: Date;
+  end: Date;
+}