WIP checkpoint: T1: Moderation data model + Alembic migration

backend/app/models/user.py

@@ -1,13 +1,21 @@
 from datetime import date
 from typing import Optional
 
-from sqlalchemy import Column, Integer, String, Boolean, DateTime, Date
+from sqlalchemy import Column, Integer, String, Boolean, DateTime, Date, func
+from sqlalchemy.dialects.postgresql import ENUM
 from sqlalchemy.orm import relationship
-from sqlalchemy.sql import func
+import enum
 
 from app.database import Base
 
 
+class UserRole(str, enum.Enum):
+    """User role for moderation and access control."""
+    USER = "user"
+    MODERATOR = "moderator"
+    ADMIN = "admin"
+
+
 class User(Base):
     __tablename__ = "users"
 
@@ -17,6 +25,13 @@ class User(Base):
     hashed_password = Column(String(255), nullable=False)
     date_of_birth = Column(Date, nullable=True)
     is_active = Column(Boolean, default=True)
+    role = Column(
+        ENUM(UserRole, name="user_role", create_type=False),
+        default=UserRole.USER,
+        nullable=False,
+    )
+    banned_until = Column(DateTime(timezone=True), nullable=True)
+    suspended_until = Column(DateTime(timezone=True), nullable=True)
     created_at = Column(DateTime(timezone=True), server_default=func.now())
     updated_at = Column(DateTime(timezone=True), onupdate=func.now())