fix: resolve nlreturn, modernize, perfsprint, wsl_v5, and partial err113 lint issues

internal/models/auth_token.go

@@ -2,7 +2,7 @@ package models
 
 import (
 	"context"
-	"fmt"
+	"errors"
 	"time"
 )
 
@@ -23,5 +23,5 @@ func (t *AuthToken) User(ctx context.Context) (*User, error) {
 		return ul.GetUserByID(ctx, t.UserID)
 	}
 
-	return nil, fmt.Errorf("user lookup not available")
+	return nil, errors.New("user lookup not available")
 }