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/models/video.py

@@ -0,0 +1,78 @@
+"""Video streaming models"""
+from sqlalchemy import Column, Integer, String, Text, Boolean, DateTime, ForeignKey, Float
+from sqlalchemy.sql import func
+from app.database import Base
+
+
+class Video(Base):
+    """Video model"""
+
+    __tablename__ = "videos"
+
+    id = Column(Integer, primary_key=True, index=True)
+    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
+
+    title = Column(String(255), nullable=False)
+    description = Column(Text)
+    thumbnail_url = Column(String(500))
+    video_url = Column(String(500), nullable=False)
+
+    # Video metadata
+    duration = Column(Integer)  # in seconds
+    resolution = Column(String(20))  # e.g., "1920x1080"
+    file_size = Column(Integer)  # in bytes
+    format = Column(String(20))  # e.g., "mp4", "webm"
+
+    # Engagement
+    views_count = Column(Integer, default=0)
+    likes_count = Column(Integer, default=0)
+    dislikes_count = Column(Integer, default=0)
+    comments_count = Column(Integer, default=0)
+
+    # Visibility
+    is_public = Column(Boolean, default=True)
+    is_live = Column(Boolean, default=False)
+    is_processing = Column(Boolean, default=False)
+
+    # Categories/Tags
+    category = Column(String(100))
+    tags = Column(Text)  # Comma-separated
+
+    # Timestamps
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now())
+    published_at = Column(DateTime(timezone=True))
+
+
+class VideoView(Base):
+    """Video view tracking"""
+
+    __tablename__ = "video_views"
+
+    id = Column(Integer, primary_key=True, index=True)
+    video_id = Column(Integer, ForeignKey("videos.id", ondelete="CASCADE"), nullable=False)
+    user_id = Column(Integer, ForeignKey("users.id", ondelete="SET NULL"))
+
+    # Watch metadata
+    watch_duration = Column(Integer)  # seconds watched
+    completion_percentage = Column(Float)
+
+    # Analytics
+    ip_address = Column(String(45))
+    user_agent = Column(String(500))
+    referrer = Column(String(500))
+
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+
+class VideoLike(Base):
+    """Video like/dislike tracking"""
+
+    __tablename__ = "video_likes"
+
+    id = Column(Integer, primary_key=True, index=True)
+    video_id = Column(Integer, ForeignKey("videos.id", ondelete="CASCADE"), nullable=False)
+    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
+    is_like = Column(Boolean, default=True)  # True=like, False=dislike
+
+    created_at = Column(DateTime(timezone=True), server_default=func.now())