Add comprehensive README for NewHacks 2025 hackathon project

[Copilot]

Added root-level README.md to document the AtlasTalk conversational AI platform built for NewHacks 2025.

Content

• Project overview: Conversational AI for practicing real-world scenarios across cultural contexts
• Tech stack: FastAPI + MongoDB + Gemini AI backend; Next.js + React + TypeScript frontend
• Setup instructions: Backend (Python dependencies, environment config, server startup) and frontend (npm install, dev server)
• API documentation: Conversation, audio, and agent endpoints with curl examples
• Available scenarios: 15+ pre-configured agents (TAXI, BARISTA, COLLEGE, etc.)
• Configuration: Text-only vs audio mode, environment variables
• Project structure: Directory tree showing backend services/routes/models and frontend app/components
• Troubleshooting: Common issues (audio, CORS, database, API keys)

No emojis used per requirements—only standard box-drawing characters for tree visualization.

Original prompt

On /, add a readme file for our NewHacks 2025 hackathon project. with no emojis

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