Applies several stock adjustments and moves in one call, all or nothing.

Requires ManageInventory and an Idempotency-Key header (one key covers the whole batch). Each operation follows the rules of POST /api/v1/items/{id}/stock/adjust ("action": "Adjust") or /stock/move ("action": "Move"). Operations apply in order, so a later removal can use units an earlier one added. Every operation is checked before anything is written, and the writes share one transaction: if any operation fails, nothing changes and the problem's detail starts with operations[i] naming the first failing one (also in the failedIndex extension). 1..100 operations, at most 1000 units in total. Example: <c>{ "operations": [ { "action": "Adjust", "itemId": 12, "locationId": 3, "delta": 10 }, { "action": "Move", "itemId": 12, "fromLocationId": 3, "toLocationId": 4, "quantity": 2 } ] }</c>.