Correct PLAYER_FIELD_INV_SLOT_HEAD default from 322 to 324 (UNIT_END+0xB0)
which was shifting every equipment slot by one position. Fix auto-detection
to validate against known 3.3.5a base. Change CMSG_AUTOEQUIP_ITEM to send
uint8 bag+slot instead of uint64 GUID, and add slot offset 23 for backpack
items in both auto-equip and use-item packets.