fix: update UserRole references to lowercase in admin.py

backend/app/api/routes/admin.py

@@ -15,7 +15,7 @@ async def get_queue(
     db: AsyncSession = Depends(get_db),
     _: User = Depends(get_admin_user),
 ):
-    result = await db.execute(select(User).where(User.role == UserRole.PENDING))
+    result = await db.execute(select(User).where(User.role == UserRole.pending))
     return result.scalars().all()
 
 
@@ -42,7 +42,7 @@ async def approve_user(
     user = result.scalar_one_or_none()
     if not user:
         raise HTTPException(status_code=404, detail="User not found")
-    user.role = UserRole.APPROVED
+    user.role = UserRole.approved
     await db.commit()
     await db.refresh(user)
     return user