Read item_type through the cache template bridge

Every consumer of the legacy ItemTemplate item_type now reads
template.cacheTemplate.getItemType(). Left on the legacy field: the
type count in dbItemHandler.LOAD_ITEM_TEMPLATES, which runs before the
bridge is linked. The charter checks already read DeedTemplate.

Parity (offline, static_item_templates vs the template
CObjectIndex.lookup picks, scripts/p14.py, 7586 templates: ITEM 4011,
DEED 880, RUNE 2695): 0 differences in item_type. No value changes
expected.

JSON-Refactor-Plan Task 1.4.

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.item_type.equals(ItemType.GOLD)) {
+                if (item.template.cacheTemplate.getItemType().equals(ItemType.GOLD)) {
                     if (item.getNumOfItems() == 0)
                         continue;
                 }