fix: illegible text in modal due to wrong background color

[matthiasn]

From Copilot:
This pull request includes several changes to improve the ModalUtils class and its usage in the project, along with a version update in the pubspec.yaml file. The most important changes include fixing a context parameter, updating modal background color, adding comprehensive tests for ModalUtils, and updating the project version.

Improvements to ModalUtils:

• lib/features/surveys/tools/run_surveys.dart: Fixed the context parameter in the pageListBuilder method to use the correct context.
• lib/utils/modals.dart: Updated the modal background color to use surfaceContainerHigh instead of surfaceContainerLow.

Tests for ModalUtils:

• test/utils/modals_test.dart: Added comprehensive widget tests for ModalUtils, including tests for modalTypeBuilder, modalSheetPage, and showSinglePageModal.

Version update:

• pubspec.yaml: Updated the project version from 0.9.567+2874 to 0.9.567+2875.