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/app/(tabs)/chat.tsx

@@ -5,7 +5,7 @@ import Header from "../../components/Header";
 import BaseBackground from "../../components/BaseBackground";
 import { FlashList } from "@shopify/flash-list";
 import { ChatService } from "../../services";
-import { ProposedEventChange } from "@caldav/shared";
+import { ProposedEventChange, CreateEventDTO } from "@caldav/shared";
 import { ProposedEventCard } from "../../components/ProposedEventCard";
 
 // TODO: better shadows for everything
@@ -39,7 +39,8 @@ const Chat = () => {
   const handleEventResponse = async (
     action: "confirm" | "reject",
     messageId: string,
-    conversationId: string
+    conversationId: string,
+    event?: CreateEventDTO
   ) => {
     // Mark message as responded (optimistic update)
     setMessages((prev) =>
@@ -50,8 +51,8 @@ const Chat = () => {
 
     try {
       const response =
-        action === "confirm"
-          ? await ChatService.confirmEvent(conversationId, messageId)
+        action === "confirm" && event
+          ? await ChatService.confirmEvent(conversationId, messageId, event)
           : await ChatService.rejectEvent(conversationId, messageId);
 
       const botMessage: MessageData = {
@@ -111,7 +112,7 @@ const Chat = () => {
             proposedChange={item.proposedChange}
             respondedAction={item.respondedAction}
             onConfirm={() =>
-              handleEventResponse("confirm", item.id, item.conversationId!)
+              handleEventResponse("confirm", item.id, item.conversationId!, item.proposedChange?.event)
             }
             onReject={() =>
               handleEventResponse("reject", item.id, item.conversationId!)

apps/client/src/components/ProposedEventCard.tsx

@@ -40,6 +40,11 @@ export const ProposedEventCard = ({
       <Text style={{ color: currentTheme.textSecondary }}>
         {formatDateTime(event?.startTime)}
       </Text>
+      {event?.description && (
+        <Text style={{ color: currentTheme.textSecondary }} className="text-sm mt-1">
+          {event.description}
+        </Text>
+      )}
       {event?.isRecurring && (
         <Text style={{ color: currentTheme.textMuted }} className="text-sm">
           Wiederkehrend

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 (