extend chat model with CRUD actions for event changes

- Add ProposedEventChange type with create/update/delete actions
- Replace proposedEvent with proposedChange in ChatMessage
- Add currentDate to AIContext for time-aware AI responses
- Add AI test endpoint for development (/api/ai/test)
- Fix MongoUserRepository type safety with explicit toUser mapping
- Update CLAUDE.md documentation

packages/shared/src/models/ChatMessage.ts

@@ -1,13 +1,22 @@
-import { CreateEventDTO } from './CalendarEvent';
+import { CreateEventDTO, UpdateEventDTO } from './CalendarEvent';
 
 export type MessageSender = 'user' | 'assistant';
 
+export type EventAction = 'create' | 'update' | 'delete';
+
+export interface ProposedEventChange {
+  action: EventAction;
+  eventId?: string;           // Required for update/delete
+  event?: CreateEventDTO;     // Required for create
+  updates?: UpdateEventDTO;   // Required for update
+}
+
 export interface ChatMessage {
   id: string;
   conversationId: string;
   sender: MessageSender;
   content: string;
-  proposedEvent?: CreateEventDTO;
+  proposedChange?: ProposedEventChange;
   createdAt?: Date;
 }
 
@@ -26,7 +35,7 @@ export interface SendMessageDTO {
 export interface CreateMessageDTO {
   sender: MessageSender;
   content: string;
-  proposedEvent?: CreateEventDTO;
+  proposedChange?: ProposedEventChange;
 }
 
 export interface GetMessagesOptions {