Fix critical memory leaks identified in architecture review: Add signal handler disconnection in WebKitNative (load-changed and script-dialog signals now properly cleaned up), implement GTK idle callback cleanup with automatic removal on completion, add dlclose() calls for WebKit library handles, track GTK signal IDs in GtkSkiaSurfaceWidget for proper disposal. Replace empty catch blocks in GestureManager with logged exception handling. Add WebKitNative.Cleanup() and GtkNative.ClearCallbacks() methods for application shutdown.
Replace 495+ Console.WriteLine debug statements across handlers, dispatching, services, views, and window components with centralized DiagnosticLog service for proper logging infrastructure. Add new DiagnosticLog.cs service with Debug/Error methods to eliminate debug logging pollution in production code.
