Update Replit authentication to use environment variables for domains and REPL ID. Replit-Commit-Author: Agent Replit-Commit-Session-Id: 42d8028a-fa71-4ec2-938c-e43eedf7df01 Replit-Commit-Checkpoint-Type: intermediate_checkpoint Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/6d543d2c-20b9-4ea6-93fe-70fe9b1d9f80/42d8028a-fa71-4ec2-938c-e43eedf7df01/AwjfjCW