Refactor event rendering with column-based event management

Improves event rendering by integrating event filtering directly into column data sources

Key changes:
- Moves event filtering responsibility to IColumnDataSource
- Simplifies event rendering pipeline by pre-filtering events per column
- Supports both date and resource-based calendar modes
- Enhances drag and drop event update mechanism

Optimizes calendar rendering performance and flexibility

src/managers/GridManager.ts

@@ -1,6 +1,8 @@
 /**
  * GridManager - Simplified grid manager using centralized GridRenderer
  * Delegates DOM rendering to GridRenderer, focuses on coordination
+ *
+ * Note: Events are now provided by IColumnDataSource (each column has its own events)
  */
 
 import { eventBus } from '../core/EventBus';
@@ -10,7 +12,6 @@ import { GridRenderer } from '../renderers/GridRenderer';
 import { DateService } from '../utils/DateService';
 import { IColumnDataSource } from '../types/ColumnDataSource';
 import { Configuration } from '../configurations/CalendarConfig';
-import { EventManager } from './EventManager';
 
 /**
  * Simplified GridManager focused on coordination, delegates rendering to GridRenderer
@@ -23,19 +24,16 @@ export class GridManager {
   private dateService: DateService;
   private config: Configuration;
   private dataSource: IColumnDataSource;
-  private eventManager: EventManager;
 
   constructor(
     gridRenderer: GridRenderer,
     dateService: DateService,
     config: Configuration,
-    eventManager: EventManager,
     dataSource: IColumnDataSource
   ) {
     this.gridRenderer = gridRenderer;
     this.dateService = dateService;
     this.config = config;
-    this.eventManager = eventManager;
     this.dataSource = dataSource;
     this.init();
   }
@@ -82,31 +80,25 @@ export class GridManager {
   /**
    * Main render method - delegates to GridRenderer
    * Note: CSS variables are automatically updated by ConfigManager when config changes
+   * Note: Events are included in columns from IColumnDataSource
    */
   public async render(): Promise<void> {
     if (!this.container) {
       return;
     }
 
-    // Get columns from datasource - single source of truth
+    // Get columns from datasource - single source of truth (includes events per column)
     const columns = await this.dataSource.getColumns();
 
     // Set grid columns CSS variable based on actual column count
     document.documentElement.style.setProperty('--grid-columns', columns.length.toString());
 
-    // Extract dates for EventManager query
-    const dates = columns.map(col => col.data as Date);
-    const startDate = dates[0];
-    const endDate = dates[dates.length - 1];
-    const events = await this.eventManager.getEventsForPeriod(startDate, endDate);
-
-    // Delegate to GridRenderer with columns and events
+    // Delegate to GridRenderer with columns (events are inside each column)
     this.gridRenderer.renderGrid(
       this.container,
       this.currentDate,
       this.currentView,
-      columns,
-      events
+      columns
     );
 
     // Emit grid rendered event