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

CLAUDE.md

@@ -78,7 +78,9 @@ src/
 │   ├── BaseBackground.tsx      # Common screen wrapper
 │   ├── Header.tsx              # Header component
 │   ├── EventCard.tsx           # Event card for calendar display
-│   └── EventConfirmDialog.tsx  # AI-proposed event confirmation modal
+│   ├── EventConfirmDialog.tsx  # AI-proposed event confirmation modal
+│   └── ProposedEventCard.tsx   # Inline event proposal with confirm/reject buttons
+├── Themes.tsx                  # Centralized color/theme definitions
 ├── services/
 │   ├── index.ts                # Re-exports all services
 │   ├── ApiClient.ts            # HTTP client (get, post, put, delete)
@@ -159,13 +161,17 @@ src/
 ```
 src/
 ├── index.ts
-└── models/
+├── models/
+│   ├── index.ts
+│   ├── User.ts           # User, CreateUserDTO, LoginDTO, AuthResponse
+│   ├── CalendarEvent.ts  # CalendarEvent, CreateEventDTO, UpdateEventDTO
+│   ├── ChatMessage.ts    # ChatMessage, Conversation, SendMessageDTO, CreateMessageDTO,
+│   │                     # GetMessagesOptions, ChatResponse, ConversationSummary,
+│   │                     # ProposedEventChange, EventAction
+│   └── Constants.ts      # DAYS, MONTHS, Day, Month, DAY_INDEX
+└── utils/
     ├── index.ts
-    ├── User.ts           # User, CreateUserDTO, LoginDTO, AuthResponse
-    ├── CalendarEvent.ts  # CalendarEvent, CreateEventDTO, UpdateEventDTO
-    └── ChatMessage.ts    # ChatMessage, Conversation, SendMessageDTO, CreateMessageDTO,
-                          # GetMessagesOptions, ChatResponse, ConversationSummary,
-                          # ProposedEventChange, EventAction
+    └── dateHelpers.ts    # getDay() - get date for specific weekday relative to today
 ```
 
 **Key Types:**
@@ -177,6 +183,8 @@ src/
 - `CreateEventDTO`: Used for creating events AND for AI-proposed events
 - `GetMessagesOptions`: Cursor-based pagination with `before?: string` and `limit?: number`
 - `ConversationSummary`: id, lastMessage?, createdAt? (for conversation list)
+- `Day`: "Monday" | "Tuesday" | ... | "Sunday"
+- `Month`: "January" | "February" | ... | "December"
 
 ### Database Abstraction
 
@@ -230,24 +238,30 @@ MONGODB_URI=mongodb://root:mongoose@localhost:27017/calchat?authSource=admin
   - `utils/password`: hash(), compare() using bcrypt
   - `utils/jwt`: signToken() (verifyToken() pending)
   - `dotenv` integration for environment variables
+  - `ChatController`: sendMessage(), confirmEvent(), rejectEvent()
+  - `ChatService`: processMessage() with test responses, confirmEvent(), rejectEvent()
 - **Stubbed (TODO):**
   - `AuthMiddleware.authenticate()`: Currently uses fake user for testing
   - `AuthController`: refresh(), logout()
   - `AuthService`: refreshToken()
-  - All Chat and Event functionality
+  - `ChatController`: getConversations(), getConversation()
+  - `MongoChatRepository`: Database persistence for chat
+  - All Event functionality
 - **Not started:**
-  - `ChatController`, `ChatService`, `MongoChatRepository`
   - `EventController`, `EventService`, `MongoEventRepository`
-  - `ClaudeAdapter` (AI integration)
+  - `ClaudeAdapter` (AI integration - currently using test responses)
 
-**Shared:** Types and DTOs defined and exported.
+**Shared:** Types, DTOs, constants (Day, Month), and date utilities defined and exported.
 
-**Frontend:** Skeleton complete with file-based routing structure:
+**Frontend:**
 - Tab navigation (Chat, Calendar) implemented with basic UI
 - Calendar screen has month navigation and grid display (partially functional)
-- Chat screen has message list UI with FlashList (mock data only)
+- Chat screen functional with FlashList, message sending, and event confirm/reject
+- `ApiClient`: get(), post() implemented
+- `ChatService`: sendMessage(), confirmEvent(), rejectEvent() implemented
+- `ProposedEventCard`: Displays proposed events with confirm/reject buttons, theming support
+- `Themes.tsx`: Centralized color definitions including button colors
 - Auth screens (Login, Register), Event Detail, and Note screens exist as skeletons
-- Services (ApiClient, AuthService, EventService, ChatService) defined with `throw new Error('Not implemented')`
 - Zustand stores (AuthStore, EventsStore) defined with `throw new Error('Not implemented')`
 - Components (EventCard, EventConfirmDialog) exist as skeletons