feat(notebooks): Enhance STFT notebook and model selection functionality

- Updated paths in the STFT notebook to reflect new data files.
- Improved plotting aesthetics for combined plots and added grid lines.
- Introduced a 3D spectrogram visualization for better data representation.
- Refactored model training function to include error handling and model export functionality.
- Adjusted model training calls to include export paths for saved models. Closes #90
- Added additional markdown cells for better documentation and clarity in the notebook.

.vscode/settings.json

@@ -1,4 +1,7 @@
 {
-  "python.analysis.extraPaths": ["./code/src/features"],
+  "python.analysis.extraPaths": [
+    "./code/src/features",
+    "${workspaceFolder}/code/src"
+  ],
   "jupyter.notebookFileRoot": "${workspaceFolder}/code"
 }