feat: replace layer toggle with layer selector menu

- Replace ToggleMapLayerAction with SelectMapLayerAction that takes a specific layer
- Update fireMapReducer to handle SelectMapLayerAction instead of toggling
- Use PopupMenuButton with GlobalKey to open menu on button tap
- Show check icon and bold text for currently selected layer
- Menu items display layer names: OSMC Grey, OSMC, Esri Street, Esri Satellite, Esri Terrain
- Selecting a layer immediately updates Redux state and closes the menu

lib/layerSelectorMapPlugin.dart

@@ -4,7 +4,8 @@ import 'package:get_it/get_it.dart';
 import 'package:redux/redux.dart';
 
 import 'models/appState.dart';
-import 'redux/actions.dart';
+import 'models/fireMapState.dart';
+import 'redux/fireMapActions.dart';
 
 /// Layer selector widget for changing map layers
 class LayerSelectorMapPluginWidget extends StatelessWidget {
@@ -29,14 +30,62 @@ class LayerSelectorMapPluginWidget extends StatelessWidget {
   }
 
   Widget _LayerSelectorButton(Store<AppState> store) {
-    return new FloatingActionButton(
+    final key = GlobalKey<PopupMenuButtonState<FireMapLayer>>();
+
+    return PopupMenuButton<FireMapLayer>(
+      key: key,
+      initialValue: store.state.fireMapState.layer,
+      onSelected: (FireMapLayer layer) {
+        store.dispatch(SelectMapLayerAction(layer));
+      },
+      itemBuilder: (BuildContext context) {
+        return FireMapLayer.values.map((FireMapLayer layer) {
+          final isSelected = store.state.fireMapState.layer == layer;
+          return PopupMenuItem<FireMapLayer>(
+            value: layer,
+            child: Row(
+              children: [
+                Icon(
+                  isSelected ? Icons.check : Icons.check,
+                  color: isSelected ? Colors.blue : Colors.transparent,
+                  size: 20,
+                ),
+                SizedBox(width: 8),
+                Text(
+                  _getLayerName(layer),
+                  style: TextStyle(
+                    fontWeight:
+                        isSelected ? FontWeight.bold : FontWeight.normal,
+                  ),
+                ),
+              ],
+            ),
+          );
+        }).toList();
+      },
+      child: FloatingActionButton(
         backgroundColor: Colors.black26,
         mini: true,
-        child: Icon(
-          Icons.layers,
-        ),
+        child: Icon(Icons.layers),
         onPressed: () {
-          store.dispatch(new ToggleMapLayerAction());
-        });
+          key.currentState?.showButtonMenu();
+        },
+      ),
+    );
+  }
+
+  String _getLayerName(FireMapLayer layer) {
+    switch (layer) {
+      case FireMapLayer.osmcGrey:
+        return 'OSMC Grey';
+      case FireMapLayer.osmc:
+        return 'OSMC';
+      case FireMapLayer.esri:
+        return 'Esri Street';
+      case FireMapLayer.esriSatellite:
+        return 'Esri Satellite';
+      case FireMapLayer.esriTerrain:
+        return 'Esri Terrain';
+    }
   }
 }