Use a reverse-DNS bundle identifier

Stage Manager could not resolve the icon for the old mixed-case one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/app.rs

@@ -36,7 +36,7 @@ use std::sync::{Arc, Mutex, RwLock};
 use std::thread;
 use std::time::{Duration, Instant};
 
-const APP_ID: &str = "DS4Server.rfc1437.de";
+const APP_ID: &str = "de.rfc1437.ds4server";
 const METRICS_SAMPLE_INTERVAL: Duration = Duration::from_millis(200);
 
 pub(crate) struct App {