feat(tvt): rename the Lorencia event NPC to "TvT Guard"

The NPC (560) that opens the TvT registration stands in Lorencia and was seeded as
"TvT Event Gorevlisi". Renaming the seed only helps fresh databases, so update 106
renames it on existing ones too - that name is what the admin panel lists.

The name players see over its head comes from the client's own table
(Data\Local\<lang>\Npcname(<lang>).txt), not from this designation, and is changed
there separately.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/Persistence/Initialization/Updates/AddHeykelSavasiEventUpdateSeason6.cs

@@ -99,7 +99,7 @@ public class AddHeykelSavasiEventUpdateSeason6 : UpdatePlugInBase
             var npc = context.CreateNew<MonsterDefinition>();
             gameConfiguration.Monsters.Add(npc);
             npc.Number = 560;
-            npc.Designation = "TvT Event Gorevlisi";
+            npc.Designation = "TvT Guard";
             npc.NpcWindow = NpcWindow.Undefined;
             npc.ObjectKind = NpcObjectKind.PassiveNpc;
             npc.SetGuid(npc.Number);