[BUG] Clean resources before allowing user to start a new instance

[StaticSweep]

Description
The user can currently start a new bot instance while the old one is shutting down.
This can cause unexpected results with clean-up, including:

• Remote input locking down and throwing
• Mouse overlay not erasing
• Potential to start a new script while another is running

To Reproduce

1. Go to the web UI
2. Click on a script
3. Select fixed mode
4. Spam the start/stop button
5. See error

Next Steps

1. Improve state management for the ScriptInstanceManager
2. Grey out the stop button while the script is shutting down/cleaning