Add chat module skeleton

[Tim4evar]

Closes #117

Summary
This PR implements the initial skeleton for the Chat module in the BackendAcademy. This module provides the foundational structure for supporting direct messages and chat rooms.

Changes

• New Module: Created ChatModule to encapsulate all chat-related functionality.
• Interfaces: Defined ChatRoom, Message, and ChatType in chat.interface.ts to provide strong typing for chat entities.
• DTOs: Added CreateRoomDto and CreateMessageDto to standardize data input for room and message creation.
• Service: Implemented ChatService with in-memory storage for managing rooms and messages, including methods for creation and retrieval.
• Controller: Added ChatController to expose the following RESTful endpoints:
• POST /chat/rooms: Create a new chat room (direct or group).
• GET /chat/rooms: List all available chat rooms.
• GET /chat/rooms/:roomId: Fetch details for a specific room.
• POST /chat/messages: Send a new message to a room.
• GET /chat/rooms/:roomId/messages: Retrieve the message history for a specific room.
• Integration: Registered ChatModule in the root AppModule.

Motivation
This PR establishes the necessary architecture to fulfill the requirements of #117, providing a base for future enhancements such as database persistence, WebSocket support for real-time communication, and advanced room permissions.

Verification

• The ChatModule is successfully integrated into the NestJS application.
• The API endpoints are correctly mapped and follow the intended structure.

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[MaryammAli]

nice work