Refactor code for improved readability and consistency across multiple files

- Updated formatting in `drawing_toolbar.dart` for better readability, including breaking long lines and ensuring consistent indentation.
- Enhanced the `recipient_selector_sheet.dart` by adjusting line breaks and improving the layout of text styles.
- Refactored `sar_update_sheet.dart` to improve readability, including restructuring widget layouts and ensuring consistent formatting.
- Cleaned up imports and removed unnecessary lines in `widget_test.dart`.

test/widget_test.dart

@@ -5,7 +5,6 @@
 // gestures. You can also use WidgetTester to find child widgets in the widget
 // tree, read text, and verify that the values of widget properties are correct.
 
-import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import 'package:meshcore_sar_app/main.dart';