feat: track download logs (ip, browser, device, time)

backend/app/models.py

@@ -1,6 +1,7 @@
 """SQLAlchemy models."""
 from datetime import datetime
-from sqlalchemy import Column, Integer, String, DateTime, BigInteger, Text, Index
+from sqlalchemy import Column, Integer, String, DateTime, BigInteger, Text, Index, ForeignKey
+from sqlalchemy.orm import relationship
 from app.database import Base
 
 
@@ -28,3 +29,19 @@ class Video(Base):
     __table_args__ = (
         Index("ix_video_url_format_id", "url", "format_id"),
     )
+
+    logs = relationship("DownloadLog", back_populates="video", lazy="select")
+
+
+class DownloadLog(Base):
+    __tablename__ = "download_logs"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    video_id = Column(Integer, ForeignKey("videos.id", ondelete="CASCADE"), nullable=False, index=True)
+    ip = Column(String(64), default="")
+    user_agent = Column(Text, default="")
+    browser = Column(String(64), default="")    # Chrome / Firefox / Safari / Edge / …
+    device = Column(String(32), default="")     # desktop / mobile / tablet / bot
+    downloaded_at = Column(DateTime, default=datetime.utcnow, index=True)
+
+    video = relationship("Video", back_populates="logs")