fix(launcher): steady 60fps cadence to stop VRR/G-Sync flicker

The idle repaint was 500ms (~2fps), below the G-Sync/FreeSync VRR floor, so the
panel ran low-framerate compensation and every hover/animation spiked then
dropped the rate — the swinging refresh rate makes VRR displays flicker. Present
at a constant ~60fps (16ms) instead so VRR locks to one rate. Cheap for a UI
this small; vsync keeps present times regular.

src/app.rs

@@ -1804,7 +1804,15 @@ impl LauncherApp {
 
 impl eframe::App for LauncherApp {
     fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
-        ctx.request_repaint_after(std::time::Duration::from_millis(500));
+        // Present at a steady ~60 FPS while the window is open. egui is normally
+        // reactive and would idle at ~2 FPS (a 500 ms repaint), but on a G-Sync /
+        // FreeSync (VRR) display that sits below the VRR floor: the panel engages
+        // low-framerate compensation, and every hover/animation briefly spikes the
+        // rate and drops back, so the refresh rate keeps swinging and the panel
+        // visibly flickers. A constant, in-range cadence gives VRR a single rate to
+        // lock onto and removes the flicker. 16 ms is monitor-independent and cheap
+        // for a UI this small; vsync (on by default) keeps present times regular.
+        ctx.request_repaint_after(std::time::Duration::from_millis(16));
         self.drive_restart_queue();
 
         egui::TopBottomPanel::top("header")