Invoke Archive Place

Place an archive order — a money path, so it carries Idempotency-Key parity with the legacy /v2/orders/archive route it replaces. A repeat with the same key replays the first response (one order, one credit reservation).

Returns 202 Accepted (the order lands in awaiting_data), matching the legacy wire contract exactly so the cutover is invisible to every client.

Declared BEFORE the generic /op/{operation_id} route so FastAPI matches this static path first; everything else still flows through the generic dispatch.