implement chat messaging with event proposals

- Add functional chat with server communication and test responses
- Add ProposedEventCard component for confirm/reject actions
- Move Constants (Day, Month) from client to shared package
- Add dateHelpers utility for weekday calculations
- Extend Themes.tsx with button and text colors
- Update CLAUDE.md with current implementation status
- Add *.tsbuildinfo to .gitignore

apps/server/src/app.ts

@@ -15,6 +15,21 @@ const mongoUri = process.env.MONGODB_URI || 'mongodb://localhost:27017/caldav';
 // Middleware
 app.use(express.json());
 
+// CORS - only needed for web browser development
+// Native mobile apps don't send Origin headers and aren't affected by CORS
+if (process.env.NODE_ENV !== 'production') {
+  app.use((req, res, next) => {
+    res.header('Access-Control-Allow-Origin', '*');
+    res.header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
+    res.header('Access-Control-Allow-Headers', 'Content-Type, Authorization');
+    if (req.method === 'OPTIONS') {
+      res.sendStatus(200);
+      return;
+    }
+    next();
+  });
+}
+
 // Initialize repositories
 const userRepo = new MongoUserRepository();
 const eventRepo = new MongoEventRepository();

apps/server/src/controllers/ChatController.ts

@@ -1,4 +1,5 @@
 import { Response } from 'express';
+import { SendMessageDTO } from '@caldav/shared';
 import { ChatService } from '../services';
 import { AuthenticatedRequest } from '../middleware';
 
@@ -6,15 +7,36 @@ export class ChatController {
   constructor(private chatService: ChatService) {}
 
   async sendMessage(req: AuthenticatedRequest, res: Response): Promise<void> {
-    throw new Error('Not implemented');
+    try {
+      const userId = req.user!.userId;
+      const data: SendMessageDTO = req.body;
+      const response = await this.chatService.processMessage(userId, data);
+      res.json(response);
+    } catch (error) {
+      res.status(500).json({ error: 'Failed to process message' });
+    }
   }
 
   async confirmEvent(req: AuthenticatedRequest, res: Response): Promise<void> {
-    throw new Error('Not implemented');
+    try {
+      const userId = req.user!.userId;
+      const { conversationId, messageId } = req.params;
+      const response = await this.chatService.confirmEvent(userId, conversationId, messageId);
+      res.json(response);
+    } catch (error) {
+      res.status(500).json({ error: 'Failed to confirm event' });
+    }
   }
 
   async rejectEvent(req: AuthenticatedRequest, res: Response): Promise<void> {
-    throw new Error('Not implemented');
+    try {
+      const userId = req.user!.userId;
+      const { conversationId, messageId } = req.params;
+      const response = await this.chatService.rejectEvent(userId, conversationId, messageId);
+      res.json(response);
+    } catch (error) {
+      res.status(500).json({ error: 'Failed to reject event' });
+    }
   }
 
   async getConversations(req: AuthenticatedRequest, res: Response): Promise<void> {

apps/server/src/services/ChatService.ts

@@ -1,6 +1,49 @@
-import { ChatMessage, ChatResponse, SendMessageDTO, CalendarEvent, ConversationSummary, GetMessagesOptions } from '@caldav/shared';
+import { ChatMessage, ChatResponse, SendMessageDTO, ConversationSummary, GetMessagesOptions, ProposedEventChange, getDay } from '@caldav/shared';
 import { ChatRepository, EventRepository, AIProvider } from './interfaces';
 
+// Test responses array (cycles through responses)
+let responseIndex = 0;
+
+const testResponses: Array<{ content: string; proposedChange?: ProposedEventChange }> = [
+  // {{{
+  // Response 1: Meeting mit Jens - next Friday 14:00
+  {
+    content: "Alles klar! Ich erstelle dir einen Termin für das Meeting mit Jens am nächsten Freitag um 14:00 Uhr:",
+    proposedChange: {
+      action: 'create',
+      event: {
+        title: "Meeting mit Jens",
+        startTime: getDay('Friday', 1, 14, 0),
+        endTime: getDay('Friday', 1, 15, 0),
+        description: "Arbeitstreffen",
+      }
+    }
+  },
+  // Response 2: Recurring event - every Saturday 10:00
+  {
+    content: "Verstanden! Ich erstelle einen wiederkehrenden Termin: Jeden Samstag um 10:00 Uhr Badezimmer putzen:",
+    proposedChange: {
+      action: 'create',
+      event: {
+        title: "Badezimmer putzen",
+        startTime: getDay('Saturday', 1, 10, 0),
+        endTime: getDay('Saturday', 1, 11, 0),
+        isRecurring: true,
+        recurrenceRule: "FREQ=WEEKLY;BYDAY=SA",
+      }
+    }
+  },
+  // Response 3: Calendar overview (text only, no proposedChange)
+  {
+    content: "Hier sind deine Termine für die nächsten 2 Wochen:\n\n" +
+      "Freitag, 10.01. - 14:00 Uhr: Meeting mit Jens\n" +
+      "Samstag, 11.01. - 10:00 Uhr: Badezimmer putzen\n" +
+      "Samstag, 18.01. - 10:00 Uhr: Badezimmer putzen\n\n" +
+      "Insgesamt 3 Termine.",
+  },
+  // }}}
+];
+
 export class ChatService {
   constructor(
     private chatRepo: ChatRepository,
@@ -9,15 +52,38 @@ export class ChatService {
   ) {}
 
   async processMessage(userId: string, data: SendMessageDTO): Promise<ChatResponse> {
-    throw new Error('Not implemented');
+    const response = testResponses[responseIndex % testResponses.length];
+    responseIndex++;
+
+    const message: ChatMessage = {
+      id: Date.now().toString(),
+      conversationId: data.conversationId || 'temp-conv-id',
+      sender: 'assistant',
+      content: response.content,
+      proposedChange: response.proposedChange,
+    };
+
+    return { message, conversationId: message.conversationId };
   }
 
-  async confirmEvent(userId: string, conversationId: string, messageId: string): Promise<CalendarEvent> {
-    throw new Error('Not implemented');
+  async confirmEvent(userId: string, conversationId: string, messageId: string): Promise<ChatResponse> {
+    const message: ChatMessage = {
+      id: Date.now().toString(),
+      conversationId,
+      sender: 'assistant',
+      content: 'Der Vorschlag wurde angenommen.',
+    };
+    return { message, conversationId };
   }
 
-  async rejectEvent(conversationId: string, messageId: string): Promise<void> {
-    throw new Error('Not implemented');
+  async rejectEvent(userId: string, conversationId: string, messageId: string): Promise<ChatResponse> {
+    const message: ChatMessage = {
+      id: Date.now().toString(),
+      conversationId,
+      sender: 'assistant',
+      content: 'Der Vorschlag wurde abgelehnt.',
+    };
+    return { message, conversationId };
   }
 
   async getConversations(userId: string): Promise<ConversationSummary[]> {