feat(import): import consumable item inventory

SVSim.UnitTests/Controllers/AdminControllerTests.cs

@@ -195,4 +195,32 @@ public class AdminControllerTests
         Assert.That(stored.Cards.Select(c => c.Card.Id), Is.EquivalentTo(new[] { 10001002L }),
             "Full replace: the pre-seeded 10001001 must be gone, only 10001002 present.");
     }
+
+    [Test]
+    public async Task ImportViewer_imports_items_and_replaces_existing()
+    {
+        using var factory = new SVSimTestFactory();
+        const ulong steamId = 76_561_198_111_222_336UL;
+        long viewerId = await factory.SeedViewerAsync(steamId: steamId);
+        // Registers the ItemEntry master row (70001) and gives an initial owned count to be replaced.
+        await factory.SeedOwnedItemAsync(viewerId, itemId: 70001, count: 1);
+
+        using var client = factory.CreateClient();
+        var response = await client.PostAsJsonAsync("/admin/import_viewer", new ImportViewerRequest
+        {
+            SteamId = steamId,
+            Items = new List<ImportItem>
+            {
+                new() { ItemId = 70001, Count = 5 },
+                new() { ItemId = 88888, Count = 9 }, // unknown master id -> skipped silently
+            }
+        });
+
+        Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.OK),
+            await response.Content.ReadAsStringAsync());
+        Assert.That(await factory.GetOwnedItemCountAsync(viewerId, 70001), Is.EqualTo(5),
+            "Full replace: 70001 count updated to 5.");
+        Assert.That(await factory.GetOwnedItemCountAsync(viewerId, 88888), Is.EqualTo(0),
+            "Unknown item master id must not be inserted.");
+    }
 }