Delete Paddock

Removes the paddock for good — and only while nothing is filed on it.

A paddock with any record or open task cannot be removed: the request is refused with a 409 whose errors[0].detail names the counts ("North Block has 3 records and 1 open task on it — archive this paddock instead of removing it") and whose errors[0].code is asset_in_use. The counts are read inside the delete's own transaction, not from the numbers a client read earlier, so a paddock that acquired history between a client's check and its DELETE is kept rather than silently unfiled. Archive it instead (PUT { archived: true }): its records stay on the property, and the paddock stays openable from the archive drawer.

A client offers "Remove this paddock" only while record_count and open_task_count are both zero and "Archive this paddock" otherwise — and treats a 409 as the archive face, because the numbers moved under it. The movement pointers on other assets' records (from_paddock_id / to_paddock_id) are nullified when an empty paddock is removed, so no mob is left pinned to a paddock that no longer exists.