feat: implement hotspot visualization on map

- Add HotspotSeverity type and HotspotWithSeverity interface
- Implement getHotspots() method in analyticsService with severity calculation
- Add hotspot layer to MapView component with color-coded circles
- Create hotspot markers with severity icons and report count badges
- Add detailed hotspot popups showing report count, severity score, radius, and dates
- Implement hotspot toggle control in MapFilters with loading state
- Add hotspot severity legend to MapFilters
- Integrate hotspot data fetching in MapPage with sample fallback data
- Color-code hotspot boundaries: yellow (low), orange (medium/high), red (critical)
- Display hotspot statistics in interactive popups

Implements task 12: Create hotspot visualization
Requirements: 3.2, 3.3, 3.5

src/services/analyticsService.ts

@@ -1,6 +1,6 @@
 // Analytics service for API interactions
 import { apiClient } from './api';
-import type { AnalyticsSummary, TimeSeriesDataPoint, LitterTypeDistribution, QuantityAggregation } from '@/types';
+import type { AnalyticsSummary, TimeSeriesDataPoint, LitterTypeDistribution, QuantityAggregation, Hotspot, HotspotWithSeverity, HotspotSeverity } from '@/types';
 
 class AnalyticsService {
   /**
@@ -91,6 +91,39 @@ class AnalyticsService {
 
     return response.blob();
   }
+
+  /**
+   * Get hotspot data for map visualization
+   */
+  async getHotspots(): Promise<HotspotWithSeverity[]> {
+    const hotspots = await apiClient.get<Hotspot[]>('/analytics/hotspots');
+    
+    // Calculate severity based on score and add to each hotspot
+    return hotspots.map(hotspot => ({
+      ...hotspot,
+      severity: this.calculateHotspotSeverity(hotspot.severityScore, hotspot.reportCount),
+    }));
+  }
+
+  /**
+   * Calculate hotspot severity based on score and report count
+   */
+  private calculateHotspotSeverity(score: number, reportCount: number): HotspotSeverity {
+    // Critical: score >= 0.8 or 20+ reports
+    if (score >= 0.8 || reportCount >= 20) {
+      return 'critical';
+    }
+    // High: score >= 0.6 or 15+ reports
+    if (score >= 0.6 || reportCount >= 15) {
+      return 'high';
+    }
+    // Medium: score >= 0.4 or 10+ reports
+    if (score >= 0.4 || reportCount >= 10) {
+      return 'medium';
+    }
+    // Low: everything else
+    return 'low';
+  }
 }
 
 export const analyticsService = new AnalyticsService();