Implement Unit and Component Tests

[jsattler]

Establish a robust suite of unit and component tests to ensure core logic stability.

Scope & Ideas:

• SettingsStore: Verify persistence of all settings, default values, and logic dependencies (e.g., changing VideoCodec resets incompatible options like Alpha Channel).
• RecorderViewModel: Test state machine (Idle -> Recording -> Stopped), timer calculations, and notification triggers.
• AssetWriter: Unit test the createVideoSettings and createAudioSettings methods to ensure they produce correct dictionaries for all Codec/Container combinations.
• CaptureEngine: Test createStreamConfiguration to ensure user settings (FPS, cursor, audio) map correctly to SCStreamConfiguration.
• Utils: Test any helper functions for file naming, time formatting, etc.