feat: initial project setup

backend/app/models.py

@@ -0,0 +1,44 @@
+"""SQLAlchemy ORM models for ELO rating tables."""
+
+from sqlalchemy import Column, DateTime, Float, Integer, String
+from sqlalchemy.sql import func
+
+from app.config import settings
+from app.database import Base
+
+
+class EloRating(Base):
+    """Tracks the current ELO rating for each listing."""
+
+    __tablename__ = "ratings"
+    __table_args__ = {"schema": settings.ELO_SCHEMA}
+
+    global_id = Column(String, primary_key=True)
+    elo_rating = Column(Float, nullable=False, default=settings.DEFAULT_ELO)
+    comparison_count = Column(Integer, nullable=False, default=0)
+    wins = Column(Integer, nullable=False, default=0)
+    losses = Column(Integer, nullable=False, default=0)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(
+        DateTime(timezone=True), server_default=func.now(), onupdate=func.now()
+    )
+
+
+class Comparison(Base):
+    """Records each pairwise comparison with ELO snapshots."""
+
+    __tablename__ = "comparisons"
+    __table_args__ = {"schema": settings.ELO_SCHEMA}
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    listing_a_id = Column(String, nullable=False)
+    listing_b_id = Column(String, nullable=False)
+    winner_id = Column(String, nullable=False)
+    elo_a_before = Column(Float, nullable=False)
+    elo_b_before = Column(Float, nullable=False)
+    elo_a_after = Column(Float, nullable=False)
+    elo_b_after = Column(Float, nullable=False)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+
+