Environnements Variables Behavior have change Beetween flowforge instance and device agent

### Current Behavior

When I declare an environment variable with a name and value in a Flowforge instance, if I haven't declared it in a device agent's environment variables, the device agent will automatically consider the variable from the Flowforge instance and use it.

### Expected Behavior

I want the variable from the Flowforge instance and the device agent to work independently. I understand that they used to function that way before, but now I need to modify the program to accommodate this new behavior.

### Steps To Reproduce

_No response_

### Environment

- FlowForge version:v1.8.0
- Node.js version: 16.20.0
- npm version:
- Platform/OS: Digital Ocean
- Browser: Chrome

### Have you provided an initial effort estimate for this issue?

I can not provide an initial effort estimate