feat(ui): implement Heartbeat on macOS

espanso-ui/src/mac/AppDelegate.h

@@ -35,5 +35,6 @@
 - (void) showNotification: (NSString *) message withDelay:(double) delay;
 - (IBAction) statusIconClick: (id) sender;
 - (IBAction) contextMenuClick: (id) sender;
+- (void) heartbeatHandler: (NSTimer *)timer;
 
 @end

espanso-ui/src/mac/AppDelegate.mm

@@ -33,6 +33,13 @@ void addSubMenu(NSMenu * parent, NSArray * items);
   }
 
   [[NSUserNotificationCenter defaultUserNotificationCenter] setDelegate:self];
+
+  // Heartbeat timer setup
+  [NSTimer scheduledTimerWithTimeInterval:1.0
+                                  target:self 
+                                selector:@selector(heartbeatHandler:)
+                                userInfo:nil
+                                 repeats:YES];
 }
 
 - (void) setIcon: (int32_t)iconIndex {
@@ -88,6 +95,14 @@ void addSubMenu(NSMenu * parent, NSArray * items);
   [[NSUserNotificationCenter defaultUserNotificationCenter] performSelector:@selector(removeDeliveredNotification:) withObject:notification afterDelay:delay];
 }
 
+- (void) heartbeatHandler: (NSTimer *)timer {
+  UIEvent event = {};
+  event.event_type = UI_EVENT_TYPE_HEARTBEAT;
+  if (event_callback && rust_instance) {
+    event_callback(rust_instance, event);
+  }
+}
+
 @end
 
 // Menu utility methods

espanso-ui/src/mac/mod.rs

@@ -32,6 +32,7 @@ const MAX_ICON_COUNT: usize = 3;
 
 const UI_EVENT_TYPE_ICON_CLICK: i32 = 1;
 const UI_EVENT_TYPE_CONTEXT_MENU_CLICK: i32 = 2;
+const UI_EVENT_TYPE_HEARTBEAT: i32 = 3;
 
 // Take a look at the native.h header file for an explanation of the fields
 #[repr(C)]
@@ -234,6 +235,9 @@ impl From<RawUIEvent> for Option<UIEvent> {
       UI_EVENT_TYPE_CONTEXT_MENU_CLICK => {
         return Some(UIEvent::ContextMenuClick(raw.context_menu_id));
       }
+      UI_EVENT_TYPE_HEARTBEAT  => {
+        return Some(UIEvent::Heartbeat);
+      }
       _ => {}
     }
 

espanso-ui/src/mac/native.h

@@ -28,6 +28,7 @@
 
 #define UI_EVENT_TYPE_ICON_CLICK 1
 #define UI_EVENT_TYPE_CONTEXT_MENU_CLICK 2
+#define UI_EVENT_TYPE_HEARTBEAT 3
 
 typedef struct {
   int32_t show_icon;