chore: change jan default data folder path to app's userData

[louis-jan]

Describe Your Changes

Currently, we are setting the Jan default data folder path to the user's home directory. It would be better to change it back to the app's appData folder, which is defined by the OS and used by the Electron app.

appData Per-user application data directory, which by default points to:
%APPDATA% on Windows
$XDG_CONFIG_HOME or ~/.config on Linux
~/Library/Application Support on macOS
userData The directory for storing your app's configuration files, which by default is the appData directory appended with your app's name. By convention files storing user data should be written to this directory, and it is not recommended to write large files here because some environments may backup this directory to cloud storage.

https://www.electronjs.org/docs/latest/api/app

So when a user does a fresh install of Jan, they will see Jan under ~/[Jan app data]/jan. They can delete either only the Jan user data folder or the entire Jan app data folder.

Also fixed an issue where users could not reset the path on the latest stable release.

Jan Data Folder Settings

Fixes Issues

• epic: Simplify Jan + Cortex folder locations #3329

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed

[Van-QA]

LGTM