feat: milestones, due dates, overdue filter, CSV export

app/models/milestone.py

@@ -0,0 +1,25 @@
+from sqlalchemy import Column, Integer, String, Text, DateTime, ForeignKey, Enum
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+from app.core.config import Base
+import enum
+
+
+class MilestoneStatus(str, enum.Enum):
+    OPEN = "open"
+    CLOSED = "closed"
+
+
+class Milestone(Base):
+    __tablename__ = "milestones"
+
+    id = Column(Integer, primary_key=True, index=True)
+    title = Column(String(255), nullable=False)
+    description = Column(Text, nullable=True)
+    status = Column(Enum(MilestoneStatus), default=MilestoneStatus.OPEN)
+    due_date = Column(DateTime(timezone=True), nullable=True)
+    project_id = Column(Integer, ForeignKey("projects.id"), nullable=False)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now())
+
+    project = relationship("Project")