* feat: add global teardown to remove test data and add registration/log-out to auth flow
* refactor(models/Conversation): index user field and add JSDoc to deleteConvos
* refactor: add user index to message schema and ensure user is saved to each Message
* refactor: add user to each saveMessage call
* fix: handle case where title is null in zod schema
* feat(e2e): ensure messages are deleted on cleanUp
* fix: set last convo for all endpoints on conversation update
* fix: enable registration for CI env
