Test Junction creation for possible elevated permissions

User Story

As a user who encounters permission errors when toggling addons, I want the app to offer to restart with administrator privileges, So that I can complete the operation without manually restarting.

Beta testers report receiving "failed to toggle addon" errors when toggling addons. The root cause is that creating/removing NTFS junctions requires administrator privileges on some Windows configurations.

Current Behavior

1. User toggles addon

2. Backend attempts junction create/remove

3. Windows returns "Access is denied"

4. Backend returns: "Access denied. Please run the application as administrator to create junctions."

5. Frontend displays generic error message

6. User must manually close app and restart as administrator

Desired Behavior

When a permission error occurs, the app should:

1. Detect the specific "Access denied" error

2. Prompt the user with a clear explanation

3. Offer to restart the application with elevated permissions

4. (Ideally) Resume the operation after restart