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/storage/IStore.ts

@@ -0,0 +1,18 @@
+/**
+ * IStore - Interface for IndexedDB ObjectStore definitions
+ *
+ * Each entity store implements this interface to define its schema.
+ * Enables Open/Closed Principle: IndexedDBContext works with any IStore.
+ */
+export interface IStore {
+  /**
+   * The name of the ObjectStore in IndexedDB
+   */
+  readonly storeName: string;
+
+  /**
+   * Create the ObjectStore with its schema (indexes, keyPath, etc.)
+   * Called during database upgrade (onupgradeneeded event)
+   */
+  create(db: IDBDatabase): void;
+}