fix: cast username and email to text in user repository queries

Add explicit ::text casts to username and email columns in List and Create queries to ensure proper type handling when scanning values from PostgreSQL. Update Create query to return role_id and role_name, adjusting Scan to match all returned fields.

backend/internal/user/repository.go

@@ -23,7 +23,7 @@ func NewPGRepository(db *pgxpool.Pool) *PGRepository {
 
 func (r *PGRepository) List(ctx context.Context) ([]User, error) {
 	rows, err := r.db.Query(ctx, `
-		select u.id, r.id, r.name, u.username, u.display_name, coalesce(u.email, ''), u.is_active
+		select u.id, r.id, r.name, u.username::text, u.display_name, coalesce(u.email::text, ''), u.is_active
 		from users u
 		join roles r on r.id = u.role_id
 		where u.deleted_at is null
@@ -49,12 +49,19 @@ func (r *PGRepository) Create(ctx context.Context, input CreateRequest, password
 	const query = `
 		insert into users (id, role_id, username, display_name, email, password_hash)
 		values ($1, (select id from roles where name = $2), $3, $4, nullif($5, ''), $6)
-		returning id, username, display_name, coalesce(email, ''), is_active
+		returning
+			id,
+			(select id from roles where name = $2),
+			$2,
+			username::text,
+			display_name,
+			coalesce(email::text, ''),
+			is_active
 	`
 
 	item := User{RoleName: input.Role}
 	err := r.db.QueryRow(ctx, query, uuid.New(), input.Role, input.Username, input.DisplayName, input.Email, passwordHash).
-		Scan(&item.ID, &item.Username, &item.DisplayName, &item.Email, &item.IsActive)
+		Scan(&item.ID, &item.RoleID, &item.RoleName, &item.Username, &item.DisplayName, &item.Email, &item.IsActive)
 	return item, err
 }