List year-end DLA snapshots

Returns the year-end DLA snapshots, most recent period first, with optional filtering by director. Each snapshot carries the closing balance, the S455 position and deadline, and the Benefit in Kind detail. The s455Status field holds one of not_applicable, pending, payable, repaid, or reclaimed. A snapshot is created as pending when overdrawn or not_applicable when not; the move to payable, repaid, or reclaimed is recorded by a later process.