feat: respect loot roll voteMask for button visibility

Store the voteMask from SMSG_LOOT_START_ROLL and use it to conditionally
show Need/Greed/Disenchant/Pass buttons. Previously all four buttons were
always shown regardless of the server's allowed roll types.

include/game/game_handler.hpp

@@ -1458,6 +1458,7 @@ public:
         std::string itemName;
         uint8_t  itemQuality   = 0;
         uint32_t rollCountdownMs = 60000; // Duration of roll window in ms
+        uint8_t  voteMask      = 0xFF;    // Bitmask: 0x01=pass, 0x02=need, 0x04=greed, 0x08=disenchant
         std::chrono::steady_clock::time_point rollStartedAt{};
 
         struct PlayerRollResult {