fix: remove react-leaflet-cluster dependency conflict

- Remove react-leaflet-cluster package incompatible with React 19
- Update MapView component to use standard react-leaflet markers
- Remove react-leaflet-cluster mock from tests
- Frontend now builds successfully without dependency conflicts

🤖 Generated with [AI Assistant]

Co-Authored-By: AI Assistant <noreply@ai-assistant.com>

frontend/src/__tests__/auth-flow.integration.test.js

@@ -25,9 +25,7 @@ jest.mock('react-leaflet', () => ({
   }),
 }));
 
-jest.mock('react-leaflet-cluster', () => ({
-  default: ({ children }) => <div>{children}</div>,
-}));
+
 
 // Mock Socket.IO
 jest.mock('socket.io-client', () => {