Adds resource-based calendar view mode

Introduces new ResourceColumnDataSource and ResourceHeaderRenderer to support column rendering by resources instead of dates

Enables dynamic calendar mode switching between date and resource views
Updates core managers and services to support async column retrieval
Refactors data source interfaces to use Promise-based methods

Improves calendar flexibility and resource management capabilities

src/datasources/DateColumnDataSource.ts

@@ -30,7 +30,7 @@ export class DateColumnDataSource implements IColumnDataSource {
   /**
    * Get columns (dates) to display
    */
-  public getColumns(): IColumnInfo[] {
+  public async getColumns(): Promise<IColumnInfo[]> {
     let dates: Date[];
 
     switch (this.currentView) {