fix: rename UserRole enum members to lowercase to match db values

backend/app/models/user.py

@@ -1,24 +1,24 @@
 import enum
 from datetime import datetime
-from sqlalchemy import String, Boolean, Enum, DateTime
+from sqlalchemy import String, Boolean, DateTime
 from sqlalchemy.orm import Mapped, mapped_column
+from sqlalchemy import Enum as SAEnum
 from app.core.database import Base
 
 
 class UserRole(str, enum.Enum):
-    PENDING = "pending"
-    APPROVED = "approved"
-    ADMIN = "admin"
+    pending = "pending"
+    approved = "approved"
+    admin = "admin"
 
 
 class User(Base):
     __tablename__ = "users"
-
     id: Mapped[int] = mapped_column(primary_key=True)
     email: Mapped[str] = mapped_column(String(255), unique=True, nullable=False, index=True)
     hashed_password: Mapped[str] = mapped_column(String(255), nullable=False)
     display_name: Mapped[str | None] = mapped_column(String(100))
-    role: Mapped[UserRole] = mapped_column(Enum(UserRole, native_enum=False), default=UserRole.PENDING, nullable=False)
+    role: Mapped[UserRole] = mapped_column(SAEnum(UserRole), default=UserRole.pending, nullable=False)
     is_active: Mapped[bool] = mapped_column(Boolean, default=True, nullable=False)
     created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow, nullable=False)
     updated_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False)