Audacity 4: Restore “Default View Mode” preference for Spectrogram

### Problem to be solved

Audacity 3.x allowed users to set Preferences → Tracks → Default View Mode → Spectrogram, so newly imported or opened audio tracks would automatically appear in Spectrogram view.

This option appears to be missing in Audacity 4.0.0. For bioacoustics, bird-call analysis, bat-call analysis, and other spectral-analysis workflows, users may inspect many WAV files and work almost exclusively in Spectrogram view. Manually switching every new track from Waveform to Spectrogram adds repetitive steps and slows down the workflow.

### Your idea

Please restore a global preference for the default track visualization, similar to Audacity 3.x.

For example:

Default track visualization:

Waveform
Spectrogram

When Spectrogram is selected, newly imported or opened audio tracks should automatically use Spectrogram view.

This would restore the previous 3.x workflow and make Audacity 4 more efficient for scientific and bioacoustic analysis.

### Prior art

_No response_

### Additional context

_No response_

The issue names Preferences → Tracks → Default View Mode and the newly imported or opened audio-track path, but no files or tests. Start by locating Audacity 4's Tracks preferences and the code that creates imported or opened tracks, then compare the Audacity 3.x behavior. Done means a global Waveform/Spectrogram choice is restored and applied to newly imported or opened tracks.

Written by the indexing model from the issue text.