implement ngrok rtunneling

[Mike-FreeAI]

Implements ngrok tunneling to expose local development servers to the internet, enhancing the project's capability for remote access and testing.

• Updates backend/.env.example: Adds ngrok configuration options including NGROK_AUTH_TOKEN and NGROK_TUNNEL_NAME to allow developers to specify their ngrok auth token and desired tunnel name.
• Modifies backend/executor/terminal.go:
  • Imports the ngrok package to utilize its tunneling features.
  • Initializes ngrok in the TerminalName function using a placeholder auth token, aiming to create or retrieve an ngrok tunnel based on the flow ID. This replaces the previous logic of simply formatting a terminal name string.
  • Adjusts the TerminalName function to return the ngrok tunnel's public URL, enabling the use of ngrok tunnel URL for terminal connections.
• Enhances README.md:
  • Adds instructions for setting up ngrok tunneling, including obtaining an auth token and configuring the .env file with ngrok details.
  • Guides on starting the ngrok tunnel to expose the local development server to the internet, facilitating external access and sharing.

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