fix: improve error message when role command returns 404

[SimeonGriggs]

Changes

• role create - updated error message
• role list - updated error message
• role reset-default - updated error message

Before

pscale role create typo-database main app
Error: branch main does not exist in database typo-database (organization: my-org)

After

pscale role create typo-database main app
Error: database typo-database or branch main does not exist in organization my-org

Question:

This follows the pattern used in keyspace/create.go and keyspace/list.go.

An alternative approach would be to first check if the database exists (like branch/show.go does), which would allow more precise error messages. However, that adds an extra API call on the error path. Happy to implement that approach if preferred.