Sets up calendar package with core infrastructure

Adds core calendar package components including:
- Base services for events, resources, and settings
- Calendar app and orchestrator
- Build and bundling configuration
- IndexedDB storage setup

Prepares foundational architecture for calendar functionality

packages/calendar/src/extensions/departments/DepartmentService.ts

@@ -0,0 +1,25 @@
+import { IDepartment, EntityType, IEventBus } from '../../types/CalendarTypes';
+import { DepartmentStore } from './DepartmentStore';
+import { BaseEntityService } from '../../storage/BaseEntityService';
+import { IndexedDBContext } from '../../storage/IndexedDBContext';
+
+/**
+ * DepartmentService - CRUD operations for departments in IndexedDB
+ */
+export class DepartmentService extends BaseEntityService<IDepartment> {
+  readonly storeName = DepartmentStore.STORE_NAME;
+  readonly entityType: EntityType = 'Department';
+
+  constructor(context: IndexedDBContext, eventBus: IEventBus) {
+    super(context, eventBus);
+  }
+
+  /**
+   * Get departments by IDs
+   */
+  async getByIds(ids: string[]): Promise<IDepartment[]> {
+    if (ids.length === 0) return [];
+    const results = await Promise.all(ids.map(id => this.get(id)));
+    return results.filter((d): d is IDepartment => d !== null);
+  }
+}