Fix decoration reward timestamp to prevent duplicate rewards

Maple2.Model/Game/User/Home.cs

@@ -158,7 +158,6 @@ public void GainExp(long exp, IReadOnlyDictionary<int, MasteryUgcHousingTable.En
             DecorationLevel++;
         }
 
-        DecorationRewardTimestamp = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
         DecorationExp += exp;
     }
 

Maple2.Server.Game/Manager/HousingManager.cs

@@ -407,6 +407,10 @@ public void InitNewHome(string characterName, ExportedUgcMapMetadata? template)
     public void InteriorCheckIn(Plot plot) {
         if (session.Field is null) return;
 
+        if (Home.DecorationRewardTimestamp != 0) {
+            return;
+        }
+
         Dictionary<HousingCategory, int> decorationCurrent = plot.Cubes.Values
             .Where(plotCube => plotCube.Metadata.Housing != null)
             .GroupBy(plotCube => plotCube.Metadata.Housing!.HousingCategory)
@@ -468,6 +472,7 @@ public void InteriorCheckIn(Plot plot) {
         }
 
         Home.GainExp(decorationScore, tableMetadata.MasteryUgcHousingTable.Entries);
+        Home.DecorationRewardTimestamp = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
         session.Send(CubePacket.DesignRankReward(Home));
     }