A Warlock cannot place a Soulstone on another player #620

Expected (1.12.1). A Warlock uses the Soulstone item on a friendly player's target. That player gets the Soulstone Resurrection aura, not the Warlock.

Actual (at 87109e3c). The Gateway reads no target from CMSG_USE_ITEM and calls use_item with only the caster's own guid (item.rs#L210-L223). apply_item_use always casts the item's on-use spell at the caster (ops.rs#L678-L686). The Soulstone Resurrection aura is already modeled with a friendly single target, so the gap is only in how item use picks its target. There is also no item-use cooldown mechanism anywhere in the Module, so the Soulstone's 30-minute cooldown is unenforced, and a Soulstone consumed on cast start is not restored if the cast is later interrupted, the same as every other timed consumable.

How it shows. A Warlock can only Soulstone themselves; targeting another player and using the item does nothing for that player.

Fix direction. Read the client's target out of CMSG_USE_ITEM and pass it through to apply_item_use, which should cast at that target instead of the caster when the item's spell has a friendly single target. The cooldown and the interrupted-cast item loss can land in this change or be filed separately.

Refs #11, #618.