Add comprehensive messenger features and improvements

- Backend improvements: flexible user authentication, nullable fields
- Frontend enhancements: new screens (NewMessage, UserInfo), improved UI/UX
- Chat functionality: real-time messaging with polling, message actions
- Visual upgrades: gradient backgrounds, better themes, modern design
- Added project documentation (CLAUDE.md) and development guidelines

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Prism is a real-time messenger built with Expo (React Native) frontend and NestJS backend using GraphQL and PostgreSQL. The project is structured as a monorepo with separate frontend and backend directories.
+
+## Development Commands
+
+### Backend (NestJS)
+```bash
+cd backend
+npm run start:dev    # Development server with hot reload
+npm run build        # Build for production
+npm run test         # Run unit tests
+npm run test:e2e     # Run end-to-end tests
+npm run lint         # ESLint with auto-fix
+npm run format       # Prettier formatting
+```
+
+### Frontend (Expo/React Native)
+```bash
+cd frontend
+npx expo start       # Start Expo development server
+npx expo start --ios # Start with iOS simulator
+npx expo start --android # Start with Android emulator
+```
+
+## Architecture
+
+### Backend Architecture
+- **Framework**: NestJS with TypeScript
+- **API**: GraphQL using code-first approach with auto-generated schema
+- **Database**: PostgreSQL with TypeORM (synchronize enabled in development)
+- **Authentication**: JWT with Passport strategy
+- **Real-time**: GraphQL Subscriptions for live updates
+- **Module Structure**:
+  - `auth/` - JWT authentication and guards
+  - `users/` - User management and profiles
+  - `conversations/` - Chat/conversation management
+  - `messages/` - Message handling and real-time updates
+
+### Frontend Architecture
+- **Framework**: Expo with React Native and TypeScript
+- **State Management**: Apollo Client for GraphQL state management
+- **UI Framework**: React Native Paper with custom theming
+- **Navigation**: React Navigation with stack and tab navigators
+- **Storage**: AsyncStorage for token persistence
+- **Key Contexts**: AuthContext for authentication state
+
+### Data Flow
+- Frontend communicates with backend exclusively through GraphQL
+- Real-time updates via GraphQL subscriptions
+- JWT tokens stored in AsyncStorage and included in GraphQL requests via authLink
+- Apollo Client handles caching with cache-and-network fetch policy
+
+## Database Configuration
+
+The project supports both remote and local PostgreSQL:
+- Remote database is the default (configured in backend .env)
+- Local database can be enabled by uncommenting postgres service in docker-compose.yml
+- TypeORM synchronize is enabled in development (automatic schema updates)
+
+## Environment Configuration
+
+### Backend Environment Variables
+Required in `backend/.env`:
+```
+DATABASE_HOST=
+DATABASE_PORT=5432
+DATABASE_USERNAME=
+DATABASE_PASSWORD=
+DATABASE_NAME=prism_messenger
+JWT_SECRET=
+JWT_EXPIRATION=7d
+```
+
+### Frontend API Configuration
+Update `frontend/src/config/api.ts` based on development environment:
+- iOS simulator: http://localhost:3000/graphql
+- Android emulator: http://10.0.2.2:3000/graphql
+- Physical device: http://YOUR_IP:3000/graphql
+
+## Key Implementation Details
+
+- GraphQL schema is auto-generated at `backend/src/schema.gql`
+- All GraphQL queries, mutations, and subscriptions are centralized in `frontend/src/graphql/`
+- Authentication uses JWT with bearer token authorization
+- Real-time features implemented via GraphQL subscriptions with graphql-ws
+- Frontend theme system supports both light and dark modes
+- Message features include send, edit, delete with real-time updates