implement event persistence and improve Mongoose TypeScript patterns

- Add event persistence: confirmed events are now saved to MongoDB
- Refactor Mongoose models to use virtuals for id field with IdVirtual interface
- Update repositories to use toJSON() with consistent type casting
- Add more test responses for chat (doctor, birthday, gym, etc.)
- Show event description in ProposedEventCard
- Change mongo-express port to 8083
- Update CLAUDE.md with Mongoose model pattern documentation

apps/client/src/services/ChatService.ts

@@ -4,6 +4,7 @@ import {
   ChatMessage,
   ConversationSummary,
   GetMessagesOptions,
+  CreateEventDTO,
 } from "@caldav/shared";
 import { ApiClient } from "./ApiClient";
 
@@ -14,9 +15,10 @@ export const ChatService = {
 
   confirmEvent: async (
     conversationId: string,
-    messageId: string
+    messageId: string,
+    event: CreateEventDTO
   ): Promise<ChatResponse> => {
-    return ApiClient.post<ChatResponse>(`/chat/confirm/${conversationId}/${messageId}`);
+    return ApiClient.post<ChatResponse>(`/chat/confirm/${conversationId}/${messageId}`, event);
   },
 
   rejectEvent: async (