POL-10: Add rules table

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/models/rule.py

@@ -0,0 +1,22 @@
+import uuid
+from datetime import datetime
+
+from sqlalchemy import DateTime, ForeignKey, String, Text, Uuid, func
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.database import Base
+
+
+class Rule(Base):
+    __tablename__ = "rules"
+
+    id: Mapped[uuid.UUID] = mapped_column(Uuid(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    championship_id: Mapped[uuid.UUID] = mapped_column(Uuid(as_uuid=True), ForeignKey("championships.id", ondelete="CASCADE"), nullable=False)
+    # section: 'general' | 'costume' | 'scoring' | 'penalty'
+    section: Mapped[str] = mapped_column(String(20), nullable=False, default="general")
+    name: Mapped[str] = mapped_column(String(255), nullable=False)
+    value: Mapped[str | None] = mapped_column(Text)
+
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())
+
+    championship: Mapped["Championship"] = relationship(back_populates="rules")  # type: ignore[name-defined]