Switch Item.template and MobLoot to CObjectTemplate

Item.template is now the cache template from CObjectTemplate.lookup
instead of the legacy DB ItemTemplate, so item.template.cacheTemplate.X
becomes item.template.X. MobLoot, LootManager, ItemManager.isTwoHanded/
isShield and CombatManager.getSwingAnimation take a CObjectTemplate.

No value changes: every getter already read the cache template through
the bridge, and the lookup resolves the same 7586 ids as
static_item_templates with the same item_type (offline parity p17.py,
0 differences).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/engine/net/client/msg/VendorBuyWindowMsg.java

@@ -156,7 +156,7 @@ public class VendorBuyWindowMsg extends ClientNetMsg {
             for (Item item : inventory) {
                 if (item.getOwnerID() != ownerID)
                     continue;
-                if (item.template.cacheTemplate.getItemType().equals(ItemType.GOLD)) {
+                if (item.template.getItemType().equals(ItemType.GOLD)) {
                     if (item.getNumOfItems() == 0)
                         continue;
                 }