feat(inventory): GrantAsync handles Card + cosmetic cascade

Card grants produce a post-state-total entry and run the CardCosmeticReward
cascade (foil twin → id-1 lookup). Cascade additions are skipped when the
viewer already owns the cosmetic; missing-master-row failures are logged
and dropped without failing the parent grant.

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

SVSim.UnitTests/Infrastructure/SVSimTestFactory.cs

@@ -427,6 +427,23 @@ internal sealed class SVSimTestFactory : WebApplicationFactory<Program>
         await db.SaveChangesAsync();
     }
 
+    /// <summary>
+    /// Seeds a bare <see cref="ShadowverseCardEntry"/> (no viewer ownership) and returns its id.
+    /// Used by InventoryGrantCardTests to get a valid card id without also seeding owned state.
+    /// Ids start at 800_000_000 (non-foil) or 800_000_001 (foil) and increment by 2 per call to
+    /// keep foil twins aligned.
+    /// </summary>
+    public async Task<long> SeedCardAsync(bool isFoil = false)
+    {
+        using var scope = Services.CreateScope();
+        var ctx = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        long id = isFoil ? 800_000_001L : 800_000_000L;
+        while (await ctx.Cards.AnyAsync(c => c.Id == id)) id += 2;
+        ctx.Cards.Add(new ShadowverseCardEntry { Id = id, IsFoil = isFoil, Name = $"SeedCard{id}" });
+        await ctx.SaveChangesAsync();
+        return id;
+    }
+
     /// <summary>
     /// Sets the viewer's RedEther balance to <paramref name="amount"/>. Call this AFTER
     /// <see cref="SeedOwnedCardAsync"/>, which resets RedEther to 0. Create tests use this