Add a GET route for validate tunnel so we can use caddy on_demand

PR Summary

Addition to .gitignore We've made improvements to protect sensitive details by adding db.db to the .gitignore file. This ensures that our database doesn't inadvertently get exposed in the public code.
Updated Server Factory The app/Server/Factory.php file has been updated to handle a new route (/validate-tunnel). An additional mechanism, addValidateTunnel(), has been added to facilitate this new routing.
New File: ValidateTunnelController A new file app/Server/Http/Controllers/ValidateTunnelController.php has been introduced. This forms part of our efforts to manage new requests efficiently. It specifically deals with the handling of requests to /validate-tunnel.
Updates in configuration We've included a new configuration for validate_tunnel in the config/expose.php file. It accommodates an authorized key, therefore enhancing our security measures.