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/Services/MissionProgressServiceTests.cs

@@ -1,6 +1,7 @@
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.DependencyInjection;
 using SVSim.Database;
+using SVSim.Database.Enums;
 using SVSim.Database.Models;
 using SVSim.EmulatedEntrypoint.Services;
 using SVSim.UnitTests.Infrastructure;
@@ -95,7 +96,7 @@ public class MissionProgressServiceTests
             db.AchievementCatalog.Add(new AchievementCatalogEntry
             {
                 AchievementType = 31, Level = 3, Name = "Win 50 ranked matches",
-                RequireNumber = 50, RewardType = 9, RewardDetailId = 0, RewardNumber = 20,
+                RequireNumber = 50, RewardType = (UserGoodsType)9, RewardDetailId = 0, RewardNumber = 20,
                 OrderNum = 18, EventType = "ranked_win", EventArg = null,
             });
             // Set viewer's current level to 3.