Adds drag-drop support for calendar events

Introduces comprehensive drag-drop functionality for calendar events
- Implements DragDropManager to handle event dragging
- Adds new CoreEvents for drag-drop interactions
- Supports smooth interpolation and grid snapping
- Provides flexible event handling with ghost element strategy

src/v2/demo/DemoApp.ts

@@ -7,6 +7,7 @@ import { HeaderDrawerManager } from '../core/HeaderDrawerManager';
 import { IndexedDBContext } from '../storage/IndexedDBContext';
 import { DataSeeder } from '../workers/DataSeeder';
 import { ViewConfig } from '../core/ViewConfig';
+import { DragDropManager } from '../managers/DragDropManager';
 
 export class DemoApp {
   private animator!: NavigationAnimator;
@@ -21,7 +22,8 @@ export class DemoApp {
     private scrollManager: ScrollManager,
     private headerDrawerManager: HeaderDrawerManager,
     private indexedDBContext: IndexedDBContext,
-    private dataSeeder: DataSeeder
+    private dataSeeder: DataSeeder,
+    private dragDropManager: DragDropManager
   ) {}
 
   async init(): Promise<void> {
@@ -50,6 +52,9 @@ export class DemoApp {
     // Init header drawer
     this.headerDrawerManager.init(this.container);
 
+    // Init drag-drop
+    this.dragDropManager.init(this.container);
+
     // Setup event handlers
     this.setupNavigation();
     this.setupDrawerToggle();