博弈分析按合约分类展示，新增合约下拉选择器

ft-app/app/models.py

@@ -53,18 +53,18 @@ class DailyBar(Base):
 
 class PositionSnapshot(Base):
     __tablename__ = "position_snapshots"
-    __table_args__ = (UniqueConstraint("institution", "direction", "date"),)
+    __table_args__ = (UniqueConstraint("contract_code", "institution", "direction", "date"),)
 
     id: Mapped[int] = mapped_column(primary_key=True)
+    contract_code: Mapped[str] = mapped_column(String(10), index=True, default="FG")
     institution: Mapped[str] = mapped_column(String(20), index=True)
-    direction: Mapped[str] = mapped_column(String(10))  # "long" or "short"
+    direction: Mapped[str] = mapped_column(String(10))
     date: Mapped[date] = mapped_column(Date, index=True)
     position: Mapped[int] = mapped_column(Integer)
     delta: Mapped[int] = mapped_column(Integer, default=0)
     avg_cost: Mapped[float] = mapped_column(Float)
 
 
-
 class User(Base):
     __tablename__ = "users"