Optimizes header event handling and all-day display

Improves performance by early-exiting header event processing when no drag operation is active.
Ensures the all-day container height is re-evaluated after the mouse leaves the header area, maintaining correct layout.

src/managers/AllDayManager.ts

@@ -51,6 +51,12 @@ export class AllDayManager {
       console.log('🏗️ AllDayManager: Received request to ensure all-day container exists');
       this.ensureAllDayContainer();
     });
+
+    // Listen for header mouseleave to recalculate all-day container height
+    eventBus.on('header:mouseleave', () => {
+      console.log('🔄 AllDayManager: Received header:mouseleave, recalculating height');
+      this.checkAndAnimateAllDayHeight();
+    });
   }
 
   /**