Function list_deleted_before 

pub fn list_deleted_before(
    conn: &Connection,
    namespace: &str,
    before_ts: i64,
) -> Result<Vec<i64>, AppError>

Fetches all memory_ids in a namespace that are soft-deleted and whose deleted_at is older than before_ts (unix epoch seconds).

Used by purge to collect stale rows for permanent deletion.

Errors

Returns Err(AppError::Database) on any rusqlite failure.