Improve unit tests coverage

[lukasmatta]

Currently, unit test coverage is very low - tests are virtually non-existent. Test files exist only for the CpsFileUploadComponent and CpsAutocompleteComponent in the library and for the AppComponent in the composition.

To address this technical debt, we should aim to implement comprehensive unit tests across all components. For better visibility, we should also introduce automatic code coverage measurement, ideally integrated with pull requests to visualize coverage changes.

Current coverage of the cps-ui-kit library:

Statements	Branches	Functions	Lines
10.95%	7.59%	9.01%	11.15%
571/52137	141/1857	91/1009	542/4857

Current coverage of the composition app (app that showcases components):

Statements	Branches	Functions	Lines
2.43%	0%	0.65%	2.56%
24/984	0/143	2/304	22/857

As part of this issue:

• Increase cps-ui-kit test coverage to approximately 80% as a priority
• Implement automatic code coverage measurement (ideally with PR integration)
• Improve composition app test coverage to approximately 60%