Preserve and sanitize return path after login (#1959)
* Preserve and sanitize return path after login
Adds logic to capture, sanitize, and persist a 'next' return path through the OAuth login flow, ensuring users are redirected to their intended in-app location after authentication. Prevents open redirects by only allowing absolute in-app paths and updates both the auth and login callback logic to handle the new parameter.
* Update ChatMessage.svelte
