feat: add water quality markers to map

- Add 38 Irish beach water quality markers to map display
- Create water quality marker icons with color-coded status (excellent=green, good=blue, sufficient=amber, poor=red)
- Add water quality toggle in map filters
- Display beach name, status, and last sampled date in popups
- Create irishBeaches.ts data file with all beach locations
- Water quality markers shown by default, can be toggled off

Beaches covered: Dublin, Wicklow, Wexford, Waterford, Cork, Kerry, Clare, Galway, Mayo, Sligo, Donegal, Antrim, Down

src/pages/MapPage.tsx

@@ -5,6 +5,7 @@ import { ReportDetailModal } from '@/components/report';
 import { analyticsService } from '@/services/analyticsService';
 import { reportService } from '@/services/reportService';
 import { eventService } from '@/services/eventService';
+import { IRISH_BEACHES } from '@/data/irishBeaches';
 import type { Report, FilterState, HotspotWithSeverity, CleanupEvent, ReportResponseDTO } from '@/types';
 
 /**
@@ -20,6 +21,7 @@ export function MapPage() {
   const [showHeatmap, setShowHeatmap] = useState(false);
   const [showHotspots, setShowHotspots] = useState(false);
   const [showEvents, setShowEvents] = useState(true);
+  const [showWaterQuality, setShowWaterQuality] = useState(true);
   const [hotspots, setHotspots] = useState<HotspotWithSeverity[]>([]);
   const [isLoadingHotspots, setIsLoadingHotspots] = useState(false);
   const [reports, setReports] = useState<Report[]>([]);
@@ -452,10 +454,12 @@ export function MapPage() {
               reports={reports}
               events={showEvents ? events : []}
               hotspots={hotspots}
+              waterQuality={IRISH_BEACHES}
               filters={filters}
               showClusters={showClusters}
               showHeatmap={showHeatmap}
               showHotspots={showHotspots}
+              showWaterQuality={showWaterQuality}
               onMarkerClick={handleMarkerClick}
               onMapClick={handleMapClick}
             />
@@ -473,6 +477,8 @@ export function MapPage() {
             onToggleHotspots={handleToggleHotspots}
             showHotspots={showHotspots}
             isLoadingHotspots={isLoadingHotspots}
+            onToggleWaterQuality={() => setShowWaterQuality(!showWaterQuality)}
+            showWaterQuality={showWaterQuality}
           />
         </div>
       </div>