fix: resolve false positives for ArtStation, GeeksforGeeks, and LushStories

- ArtStation: Add urlProbe using the JSON API endpoint
  (https://www.artstation.com/users/{}.json) which returns proper
  404 for non-existing users, instead of the main page which
  returns 200 for both existing and non-existing profiles.
  Closes #2714

- GeeksforGeeks: Switch from status_code to message detection.
  Both existing and non-existing profiles return HTTP 200, but
  non-existing profiles have "false" in the page title.
  Closes #2782

- LushStories: Switch from status_code to response_url detection.
  Non-existing profiles redirect (302) to /login while existing
  profiles return 200. Closes #2371