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/Repositories/CardInventoryRepositoryTests.cs

@@ -300,7 +300,7 @@ public class CardInventoryRepositoryTests
         Assert.That(outcome.Result!.NewRedEtherTotal, Is.EqualTo(800UL), "1000 - 200 = 800");
 
         var grants = outcome.Result!.Grants;
-        Assert.That(grants.Any(g => g.RewardType == (int)UserGoodsType.Card
+        Assert.That(grants.Any(g => g.RewardType == UserGoodsType.Card
                                  && g.RewardId   == 10001001L
                                  && g.RewardNum  == 1), Is.True);
 
@@ -506,8 +506,8 @@ public class CardInventoryRepositoryTests
 
         var grants = outcome.Result!.Grants;
         // One Card grant + one Skin cascade grant
-        Assert.That(grants.Any(g => g.RewardType == (int)UserGoodsType.Card && g.RewardId == cardId), Is.True);
-        Assert.That(grants.Any(g => g.RewardType == (int)UserGoodsType.Skin && g.RewardId == skinId), Is.True);
+        Assert.That(grants.Any(g => g.RewardType == UserGoodsType.Card && g.RewardId == cardId), Is.True);
+        Assert.That(grants.Any(g => g.RewardType == UserGoodsType.Skin && g.RewardId == skinId), Is.True);
 
         var viewer = await ctx.Viewers
             .Include(v => v.LeaderSkins)