Desktop client: allow choosing install directory and data directory during installation

Summary

The desktop client currently installs to the C: drive by default. Users should be able to choose a custom install directory and a custom data directory during installation.

Requested behavior

1. Custom install directory.

   • During installation, let the user specify where the application is installed, instead of defaulting to the C: drive.

2. Custom data directory.

   • Let the user specify where app data (config, logs, cache, models, etc.) is stored, instead of defaulting to the C: drive.

Motivation

Forcing everything onto the C: drive is a pain point for users with limited space on their system drive, or who prefer to keep data on a separate partition/drive.