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/app/redis_client.py

@@ -0,0 +1,31 @@
+"""Redis client configuration"""
+import redis.asyncio as redis
+from app.config import settings
+
+# Redis connection pool
+redis_pool = None
+
+
+async def get_redis_pool():
+    """Get Redis connection pool"""
+    global redis_pool
+    if redis_pool is None:
+        redis_pool = redis.ConnectionPool.from_url(
+            settings.REDIS_URL,
+            decode_responses=True
+        )
+    return redis_pool
+
+
+async def get_redis():
+    """Get Redis client"""
+    pool = await get_redis_pool()
+    return redis.Redis(connection_pool=pool)
+
+
+async def close_redis():
+    """Close Redis connection pool"""
+    global redis_pool
+    if redis_pool:
+        await redis_pool.disconnect()
+        redis_pool = None