Removes redundant header cache invalidation

Clearing the header manager's cache on `workweek:header-update` is no longer needed, streamlining updates.

src/managers/HeaderManager.ts

@@ -132,7 +132,6 @@ export class HeaderManager {
     // Listen for workweek header updates after grid rebuild
     eventBus.on('workweek:header-update', (event) => {
       const { currentDate } = (event as CustomEvent).detail;
-      this.clearCache(); // Clear cache since DOM was cleared
       this.updateHeader(currentDate, null);
     });