Fix tray quit blocked by unconditional prevent_exit()

app_handle.exit(0) fires ExitRequested which the run callback was
unconditionally preventing. Use an AtomicBool flag so the callback
only prevents exit for hide-to-tray, not for explicit quit requests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src-tauri/src/lib.rs

@@ -1,3 +1,5 @@
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Arc;
 use tauri::{
     image::Image,
     menu::{Menu, MenuItem},
@@ -92,6 +94,9 @@ fn is_allowed_navigation(url: &Url) -> bool {
 }
 
 pub fn run() {
+    let quit_flag = Arc::new(AtomicBool::new(false));
+    let quit_flag_for_menu = quit_flag.clone();
+
     let app = tauri::Builder::default()
         .plugin(tauri_plugin_notification::init())
         .plugin(tauri_plugin_opener::init())
@@ -172,6 +177,7 @@ pub fn run() {
                         }
                     }
                     "quit" => {
+                        quit_flag_for_menu.store(true, Ordering::SeqCst);
                         app_handle.exit(0);
                     }
                     _ => {}
@@ -199,10 +205,12 @@ pub fn run() {
         .build(tauri::generate_context!())
         .expect("error building tauri application");
 
-    // -- Keep app alive when all windows are hidden --
-    app.run(|_app, event| {
+    // -- Keep app alive when all windows are hidden (but allow explicit quit) --
+    app.run(move |_app, event| {
         if let RunEvent::ExitRequested { api, .. } = event {
-            api.prevent_exit();
+            if !quit_flag.load(Ordering::SeqCst) {
+                api.prevent_exit();
+            }
         }
     });
 }