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/Controllers/SleeveControllerTests.cs

@@ -4,6 +4,7 @@ using System.Text.Json;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.DependencyInjection;
 using SVSim.Database;
+using SVSim.Database.Enums;
 using SVSim.Database.Models;
 using SVSim.UnitTests.Infrastructure;
 
@@ -44,8 +45,8 @@ public class SleeveControllerTests
                     IsEnabled = true,
                     Rewards =
                     {
-                        new SleeveShopProductRewardEntry { OrderIndex = 0, RewardType = 7, RewardDetailId = testEmblemId, RewardNumber = 1 },
-                        new SleeveShopProductRewardEntry { OrderIndex = 1, RewardType = 6, RewardDetailId = testSleeveId, RewardNumber = 1 },
+                        new SleeveShopProductRewardEntry { OrderIndex = 0, RewardType = (UserGoodsType)7, RewardDetailId = testEmblemId, RewardNumber = 1 },
+                        new SleeveShopProductRewardEntry { OrderIndex = 1, RewardType = (UserGoodsType)6, RewardDetailId = testSleeveId, RewardNumber = 1 },
                     },
                 },
             },