Credentials: Enable Anthropic API key

[vprashrex]

Is your feature request related to a problem?
The credentials section in the frontend currently does not allow users to add the Anthropic API key from the Kaapi console. This limitation hinders users from utilizing the Anthropic API effectively.

Describe the solution you'd like
Enable the frontend to accept and store the Anthropic API key.

1. Add a field for Anthropic API key in the credentials section.
2. Validate the API key format upon entry.
3. Ensure proper storage and security of the key.