Display message box on panic in Windows

There's no way to access command-line output in a Windows GUI app, so
try to display the panic message in a message box as a last resort.

crates/gui/src/bin/ntsc-rs-standalone.rs

@@ -5,5 +5,16 @@ use std::error::Error;
 use gui::app::main::run;
 
 fn main() -> Result<(), Box<dyn Error>> {
+    #[cfg(windows)]
+    std::panic::set_hook(Box::new(|info| {
+        let backtrace = std::backtrace::Backtrace::force_capture();
+        rfd::MessageDialog::new()
+            .set_buttons(rfd::MessageButtons::Ok)
+            .set_level(rfd::MessageLevel::Error)
+            .set_description(format!("{info}\n\nBacktrace:\n{backtrace}"))
+            .set_title("Error")
+            .show();
+    }));
+
     run()
 }