Validate/Remove trailing slash in host name

Problem/Motivation

$client->models() in LiteLlmAiConfigForm::validateForm will throw exception if hostname has trailing slash in it.

Steps to reproduce

Add trailing slash to working host name and it will show error message 'The API Key is invalid.'

Proposed resolution

Either update description something like 'The base URL that API requests should be made against without trailing slash.' or add validation.

Remaining tasks

User interface changes

API changes

Data model changes