fix(gift): drop RowVersion (SQLite incompatible) + restore wire reward_type map

[Timestamp] byte[] doesn't work under SQLite (the test backend) — EF
expects the DB to populate it on insert, but SQLite has no equivalent
of Postgres's xmin. The WHERE Status = Unclaimed filter plus
IInventoryService's viewer-level concurrency is the practical defense;
RowVersion was only a backstop. Regenerated the migration without the
RowVersion column.

Wire reward_type on the gift endpoint uses a gift-specific scheme that
diverges from UserGoodsType for currencies: wire 1 = Crystal (enum=2),
wire 9 = Rupy (enum=9), wire 4 = Item (enum=4). A naked cast resolves
wire 1 to UserGoodsType.RedEther and silently grants the wrong wallet
— restored the explicit WireRewardTypeToUserGoodsType map from the old
tutorial controller.

Retrofits existing GiftControllerTests to call SeedTutorialPresentsAsync
on the new helper (RegisterViewer doesn't auto-seed; only the prod
signup path does). All 7 existing tests pass.

SVSim.Database/Migrations/SVSimDbContextModelSnapshot.cs

@@ -2899,12 +2899,6 @@ namespace SVSim.Database.Migrations
                     b.Property<int>("RewardType")
                         .HasColumnType("integer");
 
-                    b.Property<byte[]>("RowVersion")
-                        .IsConcurrencyToken()
-                        .IsRequired()
-                        .ValueGeneratedOnAddOrUpdate()
-                        .HasColumnType("bytea");
-
                     b.Property<string>("Source")
                         .HasMaxLength(64)
                         .HasColumnType("character varying(64)");