fix(settings): add profile button when no profiles exist (#513)

When the LLM/Embedding/Search settings page has no profiles configured, the UI displayed 'No profiles configured. Add a profile to start.' but provided no button to actually add one. The add-profile button was only visible inside the profile editor, which never rendered when the list was empty - creating a dead end for new users.

Add a '+ Profile' button in the empty-state view, matching the existing button style used in the profile editor.

Closes #512, Closes #505