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/BattlePassControllerBuyTests.cs

@@ -37,7 +37,7 @@ public class BattlePassControllerBuyTests
         db.BattlePassRewards.Add(new BattlePassRewardEntry
         {
             Id = MakeRewardId(23, BattlePassTrack.Premium, 2),
-            SeasonId = 23, Track = BattlePassTrack.Premium, Level = 2, RewardType = 9,
+            SeasonId = 23, Track = BattlePassTrack.Premium, Level = 2, RewardType = (UserGoodsType)9,
             RewardDetailId = 0, RewardNumber = 20, IsAppealExclusion = false,
         });
         var v = await db.Viewers.FirstAsync(x => x.Id == viewerId);