feat(inventory): TrySpendAsync covers all 4 wallets + freeplay

Crystal/Rupy/RedEther freeplay no-op (returns configured amount,
balance unchanged); SpotPoint always real. Insufficient returns
current balance; success returns post-deduction balance.
SVSimTestFactory gains freeplayEnabled ctor overload that upserts
the Freeplay GameConfigSection row after EnsureSeedData.

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

SVSim.UnitTests/Services/Inventory/InventorySpendTests.cs

@@ -0,0 +1,70 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using SVSim.Database;
+using SVSim.Database.Models.Config;
+using SVSim.Database.Services;
+using SVSim.Database.Services.Inventory;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Services.Inventory;
+
+public class InventorySpendTests
+{
+    [Test]
+    public async Task Spend_sufficient_returns_post_deduction_total()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+        using var scope = factory.Services.CreateScope();
+        var ctx = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var v = await ctx.Viewers.FirstAsync(x => x.Id == viewerId);
+        v.Currency.Crystals = 1000;
+        await ctx.SaveChangesAsync();
+
+        var inv = scope.ServiceProvider.GetRequiredService<IInventoryService>();
+        await using var tx = await inv.BeginAsync(viewerId);
+        var r = await tx.TrySpendAsync(SpendCurrency.Crystal, 300);
+
+        Assert.That(r.Success, Is.True);
+        Assert.That(r.PostStateTotal, Is.EqualTo(700));
+        Assert.That(tx.Viewer.Currency.Crystals, Is.EqualTo(700UL));
+    }
+
+    [Test]
+    public async Task Spend_insufficient_returns_insufficient_with_current_balance()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+        using var scope = factory.Services.CreateScope();
+        var ctx = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var v = await ctx.Viewers.FirstAsync(x => x.Id == viewerId);
+        v.Currency.Crystals = 100;
+        await ctx.SaveChangesAsync();
+
+        var inv = scope.ServiceProvider.GetRequiredService<IInventoryService>();
+        await using var tx = await inv.BeginAsync(viewerId);
+        var r = await tx.TrySpendAsync(SpendCurrency.Crystal, 300);
+
+        Assert.That(r.Outcome, Is.EqualTo(SpendOutcome.Insufficient));
+        Assert.That(r.PostStateTotal, Is.EqualTo(100));
+        Assert.That(tx.Viewer.Currency.Crystals, Is.EqualTo(100UL), "balance unchanged");
+    }
+
+    [Test]
+    public async Task Freeplay_returns_success_with_configured_amount_for_main_currencies()
+    {
+        using var factory = new SVSimTestFactory(freeplayEnabled: true);
+        long viewerId = await factory.SeedViewerAsync();
+        using var scope = factory.Services.CreateScope();
+
+        var inv = scope.ServiceProvider.GetRequiredService<IInventoryService>();
+        await using var tx = await inv.BeginAsync(viewerId);
+        ulong balanceBefore = tx.Viewer.Currency.Crystals;
+        var r = await tx.TrySpendAsync(SpendCurrency.Crystal, 99999);
+
+        Assert.That(r.Success, Is.True);
+        var freeCfg = scope.ServiceProvider.GetRequiredService<IGameConfigService>().Get<FreeplayConfig>();
+        Assert.That(r.PostStateTotal, Is.EqualTo(checked((long)freeCfg.CurrencyAmount)));
+        Assert.That(tx.Viewer.Currency.Crystals, Is.EqualTo(balanceBefore), "freeplay never deducts");
+    }
+}