fix: chat prefix, hostile faction display, and game object looting

- Add BG_SYSTEM_NEUTRAL/ALLIANCE/HORDE chat types (0x52-0x54) and reclassify
  them as SYSTEM in the parser — prevents bogus [Say] prefix on arena/BG
  system messages
- Remove fallback [TypeName] bracket for sender-less SAY/YELL/WHISPER messages;
  only group-channel types (Party/Guild/Raid/BG) show brackets without a sender
- Remove factionTemplate != 0 guard — units with FT=0 now get setHostile() like
  any other unit (defaulting to hostile from the map default), fixing NPCs that
  appeared friendly due to unset faction template
- Enable CMSG_LOOT for WotLK type=3 (chest) game objects in addition to
  CMSG_GAMEOBJ_USE — fixes Milly's Harvest and other quest gather objects on
  AzerothCore WotLK servers

src/game/world_packets.cpp

@@ -1422,6 +1422,14 @@ bool MessageChatParser::parse(network::Packet& packet, MessageChatData& data) {
             break;
         }
 
+        case ChatType::BG_SYSTEM_NEUTRAL:
+        case ChatType::BG_SYSTEM_ALLIANCE:
+        case ChatType::BG_SYSTEM_HORDE:
+            // BG/Arena system messages — no sender GUID or name field, just message.
+            // Reclassify as SYSTEM for consistent display.
+            data.type = ChatType::SYSTEM;
+            break;
+
         default:
             // SAY, GUILD, PARTY, YELL, WHISPER, WHISPER_INFORM, RAID, etc.
             // All have receiverGuid (typically senderGuid repeated)