fix: persist dark mode theme after page reload (#2730)

src/app/settings/settings.service.ts

@@ -255,11 +255,11 @@ export class SettingsService {
     });
   }
 
-  setThemeDarkEnabled(enabled: string) {
-    localStorage.setItem('mifosXThemeDarkEnabled', enabled);
+  setThemeDarkEnabled(enabled: boolean) {
+    localStorage.setItem('mifosXThemeDarkEnabled', JSON.stringify(enabled));
   }
 
-  get themeDarkEnabled() {
+  get themeDarkEnabled(): boolean {
     return JSON.parse(localStorage.getItem('mifosXThemeDarkEnabled'));
   }
 }