首个可运行的版本

backend/app/models/system_config.py

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+"""系统配置模型"""
+
+from datetime import datetime, timezone
+
+from sqlalchemy import String, Text, DateTime, ForeignKey
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.database import Base
+
+
+class SystemConfig(Base):
+    __tablename__ = "system_configs"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True)
+    key: Mapped[str] = mapped_column(String(100), unique=True, nullable=False, index=True)
+    value: Mapped[str] = mapped_column(Text, nullable=False)
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime,
+        default=lambda: datetime.utcnow(),
+        onupdate=lambda: datetime.utcnow(),
+    )
+    updated_by: Mapped[str | None] = mapped_column(
+        String(36), ForeignKey("users.id", ondelete="SET NULL"), nullable=True
+    )