fix(deploy): improve error message when deployment already exists

[vikram-2101]

Currently the CLI shows a generic "Request failed with status code 400"
when redeploying an existing deployment.

This change checks the API response indicating that the deployment
already exists and displays a clearer message to the user.

Example:

Before:
Error: Request failed with status code 400

After:

Deployment "<name>" already exists.
Use --force to redeploy or --delete to remove it.

[viferga]

It has no tests, I won't merge it.