test(core): add comprehensive test suites for core utilities and widgets

- Implement tests for DateTime and String utility extensions
- Add widget tests for ErrorWidget and EmptyWidget components
- Include network status and token storage service tests
- Update local.properties to use debug build mode

android/local.properties

@@ -1,5 +1,5 @@
-sdk.dir=C:\\Users\\Housh11\\AppData\\Local\\Android\\sdk
+sdk.dir=C:/Users/Housh11/AppData/Local/Android/Sdk
 flutter.sdk=C:\\src\\flutter
-flutter.buildMode=release
+flutter.buildMode=debug
 flutter.versionName=1.3.26
 flutter.versionCode=23