Implement SignalR hub call to stop automation

[gravity-api]

There is a TODO in src/clients/g4-signalr-client.ts indicating the need to implement a SignalR hub call to stop automation. The current stopAutomation method is a placeholder and only logs a warning.

Relevant code section:

// TODO: Implement SignalR hub call to stop automation
console.warn('Stop-Automation is not implemented yet.');

Suggested action:

• Implement the SignalR hub method invocation to properly stop automation on the G4 hub.
• Replace the placeholder warning with the actual implementation.

File: src/clients/g4-signalr-client.ts