feat(inventory): BackfillCardCosmeticsAsync

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.Database/Services/Inventory/InventoryTransaction.cs

@@ -200,8 +200,42 @@ internal sealed class InventoryTransaction : IInventoryTransaction
         }
     }
 
-    public Task<int> BackfillCardCosmeticsAsync(CancellationToken ct = default)
-        => throw new NotImplementedException();
+    public async Task<int> BackfillCardCosmeticsAsync(CancellationToken ct = default)
+    {
+        ThrowIfCommitted();
+
+        var lookupIds = Viewer.Cards
+            .Select(c => c.Card.IsFoil ? c.Card.Id - 1 : c.Card.Id)
+            .Distinct()
+            .ToList();
+
+        var cascade = await _db.CardCosmeticRewards
+            .Where(r => lookupIds.Contains(r.CardId))
+            .ToListAsync(ct);
+
+        int granted = 0;
+        foreach (var reward in cascade)
+        {
+            if (AlreadyOwnsCosmetic(reward.Type, reward.CosmeticId)) continue;
+            if (TryAddCascadeCosmetic(reward, reward.CardId))
+            {
+                granted++;
+                _ops.Add(new GrantOp((UserGoodsType)(int)reward.Type, reward.CosmeticId, 1, 1, true));
+            }
+        }
+
+        return granted;
+    }
+
+    private bool AlreadyOwnsCosmetic(CosmeticType type, long id) => type switch
+    {
+        CosmeticType.Sleeve   => Viewer.Sleeves.Any(s => s.Id == id),
+        CosmeticType.Emblem   => Viewer.Emblems.Any(e => e.Id == id),
+        CosmeticType.Skin     => Viewer.LeaderSkins.Any(s => s.Id == id),
+        CosmeticType.Degree   => Viewer.Degrees.Any(d => d.Id == id),
+        CosmeticType.MyPageBG => Viewer.MyPageBackgrounds.Any(b => b.Id == id),
+        _ => false,
+    };
 
     public long EffectiveBalance(SpendCurrency currency) => throw new NotImplementedException();
     public bool OwnsCard(long cardId) => throw new NotImplementedException();