Fix audio volume UI indicator under silent system environments

[temcguir]

During video recording, Jetpack Camera visually indicates whether the audio stream is currently capturing sound. Previously, this indicator relied solely on checking if the audio amplitude was strictly greater than 0.0. However, in certain environments (like cuttlefish emulators) or completely silent physical spaces, CameraX can report an active audio stream that accurately returns an amplitude of 0.0 or a state of AUDIO_STATE_SOURCE_SILENCED.

This PR decouples the audio stream status from its mathematical amplitude by:

1. Introducing AudioStreamState as a modeled state corresponding to androidx.camera.video.AudioStats.
2. Tracking isAudioStreamActive alongside the numerical amplitude inside AudioUiState.
3. Updating the CaptureScreenComponents to display the active microphone toggle if the stream is confirmed active, even if the realtime amplitude happens to be zero.

[gemini-code-assist]

Code Review

This pull request refactors video recording states to use a new AudioStreamState sealed interface instead of a raw amplitude value, allowing more granular tracking of the audio stream (e.g., active, silenced, muted). However, several critical issues were identified: throwing an IllegalStateException on duplicate start events combined with enabling the capture button during the initialization phase creates a high risk of application crashes due to race conditions. Additionally, the logic for isAudioStreamActive should be updated to include the Silenced state to support silent environments properly, and the KDoc for AudioUiState.Enabled.On needs to be updated to document the new parameter.