Function insert_row 

pub async fn insert_row(
    table: &str,
    columns: &[ColumnInfo],
    values: &[(String, Value)],
) -> Result<(), AppError>

Inserts one row. values keys not found in columns are silently ignored (a form field the caller shouldn’t have sent) rather than erroring - the caller (the HTTP handler) only ever builds values from columns in the first place, so this is a defense-in-depth backstop, not the primary guard.