Add comprehensive FastAPI backend for BlackRoad OS

This commit adds a complete backend infrastructure with:

**Core Infrastructure:**
- FastAPI application with async/await support
- PostgreSQL database with SQLAlchemy ORM
- Redis caching layer
- JWT authentication and authorization
- Docker and Docker Compose configuration

**API Services:**
- Authentication API (register, login, JWT tokens)
- RoadMail API (email service with folders, send/receive)
- BlackRoad Social API (posts, comments, likes, follows)
- BlackStream API (video streaming with views/likes)
- File Storage API (file explorer with upload/download)
- RoadCoin Blockchain API (mining, transactions, wallet)
- AI Chat API (conversations with AI assistant)

**Database Models:**
- User accounts with wallet integration
- Email and folder management
- Social media posts and engagement
- Video metadata and analytics
- File storage with sharing
- Blockchain blocks and transactions
- AI conversation history

**Features:**
- Complete CRUD operations for all services
- Real-time blockchain mining with proof-of-work
- Transaction validation and wallet management
- File upload with S3 integration (ready)
- Social feed with engagement metrics
- Email system with threading support
- AI chat with conversation persistence

**Documentation:**
- Comprehensive README with setup instructions
- API documentation (Swagger/ReDoc auto-generated)
- Deployment guide for multiple platforms
- Testing framework with pytest

**DevOps:**
- Docker containerization
- Docker Compose for local development
- Database migrations with Alembic
- Health check endpoints
- Makefile for common tasks

All APIs are production-ready with proper error handling,
input validation, and security measures.

backend/tests/test_auth.py

@@ -0,0 +1,83 @@
+"""Authentication tests"""
+import pytest
+from httpx import AsyncClient
+
+
+@pytest.mark.asyncio
+async def test_register_user(client: AsyncClient):
+    """Test user registration"""
+    user_data = {
+        "username": "newuser",
+        "email": "newuser@example.com",
+        "password": "password123",
+        "full_name": "New User"
+    }
+
+    response = await client.post("/api/auth/register", json=user_data)
+    assert response.status_code == 201
+
+    data = response.json()
+    assert data["username"] == "newuser"
+    assert data["email"] == "newuser@example.com"
+    assert "wallet_address" in data
+    assert data["balance"] == 100.0  # Starting bonus
+
+
+@pytest.mark.asyncio
+async def test_register_duplicate_user(client: AsyncClient, test_user):
+    """Test registering duplicate user"""
+    user_data = {
+        "username": "testuser",
+        "email": "test@example.com",
+        "password": "password123"
+    }
+
+    response = await client.post("/api/auth/register", json=user_data)
+    assert response.status_code == 400
+
+
+@pytest.mark.asyncio
+async def test_login(client: AsyncClient, test_user):
+    """Test user login"""
+    login_data = {
+        "username": "testuser",
+        "password": "testpassword123"
+    }
+
+    response = await client.post("/api/auth/login", data=login_data)
+    assert response.status_code == 200
+
+    data = response.json()
+    assert "access_token" in data
+    assert "refresh_token" in data
+    assert data["token_type"] == "bearer"
+
+
+@pytest.mark.asyncio
+async def test_login_invalid_credentials(client: AsyncClient, test_user):
+    """Test login with invalid credentials"""
+    login_data = {
+        "username": "testuser",
+        "password": "wrongpassword"
+    }
+
+    response = await client.post("/api/auth/login", data=login_data)
+    assert response.status_code == 401
+
+
+@pytest.mark.asyncio
+async def test_get_current_user(client: AsyncClient, auth_headers):
+    """Test getting current user info"""
+    response = await client.get("/api/auth/me", headers=auth_headers)
+    assert response.status_code == 200
+
+    data = response.json()
+    assert data["username"] == "testuser"
+    assert data["email"] == "test@example.com"
+
+
+@pytest.mark.asyncio
+async def test_get_current_user_unauthorized(client: AsyncClient):
+    """Test getting current user without token"""
+    response = await client.get("/api/auth/me")
+    assert response.status_code == 401