refactor: type reward_type columns as UserGoodsType enum

Replace bare `int RewardType` on 12 catalog/reward entities and GrantedReward
with the existing UserGoodsType enum. Verified against the decompiled client:
every wire reward_type decodes through the single Wizard.UserGoods.Type enum, so
one enum is correct across all endpoint families (item_type is a separate
Item.Type axis, left untouched). EF stores the enum as the same int column, so
there is no migration.

- Importers cast seed int -> UserGoodsType at the ingest boundary.
- New GrantedReward.ToRewardList() extension replaces 8 copy-pasted
  GrantedReward -> RewardListEntry projections.
- Fix 3 .ToString() sites that would otherwise emit enum names ("Crystal")
  instead of the int wire value ("2").
- Wire DTOs keep int; the enum is widened to int at the wire boundary only.

Build green; 962/962 tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

SVSim.UnitTests/Importers/SleeveShopImporterTests.cs

@@ -2,6 +2,7 @@ using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.DependencyInjection;
 using SVSim.Bootstrap.Importers;
 using SVSim.Database;
+using SVSim.Database.Enums;
 using SVSim.Database.Models;
 using SVSim.UnitTests.Infrastructure;
 
@@ -72,7 +73,7 @@ public class SleeveShopImporterTests
         int originalCount = product.Rewards.Count;
         product.Rewards.Add(new SleeveShopProductRewardEntry
         {
-            OrderIndex = 99, RewardType = 99, RewardDetailId = 99, RewardNumber = 99,
+            OrderIndex = 99, RewardType = (UserGoodsType)99, RewardDetailId = 99, RewardNumber = 99,
         });
         await db.SaveChangesAsync();
 
@@ -82,6 +83,6 @@ public class SleeveShopImporterTests
             .Include(p => p.Rewards)
             .FirstAsync(p => p.Id == product.Id);
         Assert.That(reloaded.Rewards.Count, Is.EqualTo(originalCount), "extra reward should be wiped on re-import");
-        Assert.That(reloaded.Rewards.Any(r => r.RewardType == 99), Is.False);
+        Assert.That(reloaded.Rewards.Any(r => r.RewardType == (UserGoodsType)99), Is.False);
     }
 }