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/BaseEntityService.ts

@@ -0,0 +1,181 @@
+import { ISync, EntityType, SyncStatus, IEventBus, IEntitySavedPayload, IEntityDeletedPayload } from '../types/CalendarTypes';
+import { IEntityService } from './IEntityService';
+import { SyncPlugin } from './SyncPlugin';
+import { IndexedDBContext } from './IndexedDBContext';
+import { CoreEvents } from '../constants/CoreEvents';
+import { diff } from 'json-diff-ts';
+
+/**
+ * BaseEntityService<T extends ISync> - Abstract base class for all entity services
+ *
+ * PROVIDES:
+ * - Generic CRUD operations (get, getAll, save, delete)
+ * - Sync status management (delegates to SyncPlugin)
+ * - Serialization hooks (override in subclass if needed)
+ */
+export abstract class BaseEntityService<T extends ISync> implements IEntityService<T> {
+  abstract readonly storeName: string;
+  abstract readonly entityType: EntityType;
+
+  private syncPlugin: SyncPlugin<T>;
+  private context: IndexedDBContext;
+  protected eventBus: IEventBus;
+
+  constructor(context: IndexedDBContext, eventBus: IEventBus) {
+    this.context = context;
+    this.eventBus = eventBus;
+    this.syncPlugin = new SyncPlugin<T>(this);
+  }
+
+  protected get db(): IDBDatabase {
+    return this.context.getDatabase();
+  }
+
+  /**
+   * Serialize entity before storing in IndexedDB
+   */
+  protected serialize(entity: T): unknown {
+    return entity;
+  }
+
+  /**
+   * Deserialize data from IndexedDB back to entity
+   */
+  protected deserialize(data: unknown): T {
+    return data as T;
+  }
+
+  /**
+   * Get a single entity by ID
+   */
+  async get(id: string): Promise<T | null> {
+    return new Promise((resolve, reject) => {
+      const transaction = this.db.transaction([this.storeName], 'readonly');
+      const store = transaction.objectStore(this.storeName);
+      const request = store.get(id);
+
+      request.onsuccess = () => {
+        const data = request.result;
+        resolve(data ? this.deserialize(data) : null);
+      };
+
+      request.onerror = () => {
+        reject(new Error(`Failed to get ${this.entityType} ${id}: ${request.error}`));
+      };
+    });
+  }
+
+  /**
+   * Get all entities
+   */
+  async getAll(): Promise<T[]> {
+    return new Promise((resolve, reject) => {
+      const transaction = this.db.transaction([this.storeName], 'readonly');
+      const store = transaction.objectStore(this.storeName);
+      const request = store.getAll();
+
+      request.onsuccess = () => {
+        const data = request.result as unknown[];
+        const entities = data.map(item => this.deserialize(item));
+        resolve(entities);
+      };
+
+      request.onerror = () => {
+        reject(new Error(`Failed to get all ${this.entityType}s: ${request.error}`));
+      };
+    });
+  }
+
+  /**
+   * Save an entity (create or update)
+   * Emits ENTITY_SAVED event with operation type and changes (diff for updates)
+   * @param entity - Entity to save
+   * @param silent - If true, skip event emission (used for seeding)
+   */
+  async save(entity: T, silent = false): Promise<void> {
+    const entityId = (entity as unknown as { id: string }).id;
+    const existingEntity = await this.get(entityId);
+    const isCreate = existingEntity === null;
+
+    // Calculate changes: full entity for create, diff for update
+    let changes: unknown;
+    if (isCreate) {
+      changes = entity;
+    } else {
+      const existingSerialized = this.serialize(existingEntity);
+      const newSerialized = this.serialize(entity);
+      changes = diff(existingSerialized, newSerialized);
+    }
+
+    const serialized = this.serialize(entity);
+
+    return new Promise((resolve, reject) => {
+      const transaction = this.db.transaction([this.storeName], 'readwrite');
+      const store = transaction.objectStore(this.storeName);
+      const request = store.put(serialized);
+
+      request.onsuccess = () => {
+        // Only emit event if not silent (silent used for seeding)
+        if (!silent) {
+          const payload: IEntitySavedPayload = {
+            entityType: this.entityType,
+            entityId,
+            operation: isCreate ? 'create' : 'update',
+            changes,
+            timestamp: Date.now()
+          };
+          this.eventBus.emit(CoreEvents.ENTITY_SAVED, payload);
+        }
+        resolve();
+      };
+
+      request.onerror = () => {
+        reject(new Error(`Failed to save ${this.entityType} ${entityId}: ${request.error}`));
+      };
+    });
+  }
+
+  /**
+   * Delete an entity
+   * Emits ENTITY_DELETED event
+   */
+  async delete(id: string): Promise<void> {
+    return new Promise((resolve, reject) => {
+      const transaction = this.db.transaction([this.storeName], 'readwrite');
+      const store = transaction.objectStore(this.storeName);
+      const request = store.delete(id);
+
+      request.onsuccess = () => {
+        const payload: IEntityDeletedPayload = {
+          entityType: this.entityType,
+          entityId: id,
+          operation: 'delete',
+          timestamp: Date.now()
+        };
+        this.eventBus.emit(CoreEvents.ENTITY_DELETED, payload);
+        resolve();
+      };
+
+      request.onerror = () => {
+        reject(new Error(`Failed to delete ${this.entityType} ${id}: ${request.error}`));
+      };
+    });
+  }
+
+  // Sync methods - delegate to SyncPlugin
+  async markAsSynced(id: string): Promise<void> {
+    return this.syncPlugin.markAsSynced(id);
+  }
+
+  async markAsError(id: string): Promise<void> {
+    return this.syncPlugin.markAsError(id);
+  }
+
+  async getSyncStatus(id: string): Promise<SyncStatus | null> {
+    return this.syncPlugin.getSyncStatus(id);
+  }
+
+  async getBySyncStatus(syncStatus: string): Promise<T[]> {
+    return this.syncPlugin.getBySyncStatus(syncStatus);
+  }
+}