feat(items): catalog import with Type + ThumbnailPath columns

ItemEntry gains Type (client item_type enum, 1=challenge, 2=card-pack
ticket, 3=premium orb, 4=colosseum, 5=orb piece, 6=skin/event ticket,
7=other) and ThumbnailPath. ItemImporter mirrors PaymentItemImporter
shape: find-or-create per item_id, save once, idempotent. Wired into
Bootstrap.Program and SVSimTestFactory.SeedGlobalsAsync. Unblocks
/item_purchase/info (filters card-pack tickets by Type==2) and any
reward grant of UserGoodsType.Item, which previously threw because
the catalog was empty.

466 tests pass (was 461).

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

SVSim.Database/Migrations/SVSimDbContextModelSnapshot.cs

@@ -1095,6 +1095,13 @@ namespace SVSim.Database.Migrations
                         .IsRequired()
                         .HasColumnType("text");
 
+                    b.Property<string>("ThumbnailPath")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<int>("Type")
+                        .HasColumnType("integer");
+
                     b.HasKey("Id");
 
                     b.ToTable("Items");