During custom endpoint setup, users are now asked for a display name
with the auto-generated name as the default. Typing 'Ollama' or
'LM Studio' replaces the generic 'Local (localhost:11434)' in the
provider menu.
Extracts _auto_provider_name() for reuse and adds a name= parameter
to _save_custom_provider() so the caller can pass through the
user-chosen label.
