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/PuzzleSeedingPipelineTests.cs

@@ -53,7 +53,7 @@ public class PuzzleSeedingPipelineTests
         Assert.That(round1.TargetPuzzleGroupId, Is.EqualTo(301));
         Assert.That(round1.AchievedMessage, Is.EqualTo("Cleared all Round 1 puzzles"));
         Assert.That(round1.RequireNumber, Is.EqualTo(3));
-        Assert.That(round1.RewardType, Is.EqualTo(10));        // LeaderSkin
+        Assert.That((int)round1.RewardType, Is.EqualTo(10));        // LeaderSkin
         Assert.That(round1.RewardDetailId, Is.EqualTo(3704L)); // chara_id matching group 301
         Assert.That(round1.RewardNumber, Is.EqualTo(1));