后端开发完成

backend/app/models/project_history.py

@@ -0,0 +1,17 @@
+from sqlalchemy import Column, Integer, String, Text, DateTime, ForeignKey
+from sqlalchemy.sql import func
+from app.database.database import Base
+
+
+class ProjectHistory(Base):
+    """项目历史记录模型"""
+    __tablename__ = "project_histories"
+    
+    id = Column(Integer, primary_key=True, index=True)
+    project_id = Column(Integer, ForeignKey("projects.id"), nullable=False)
+    changed_by = Column(Integer, ForeignKey("users.id"), nullable=False)
+    change_field = Column(String(100), nullable=False)
+    old_value = Column(Text)
+    new_value = Column(Text)
+    change_description = Column(Text)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())