feat(repo): GetStoryDecksByClass joins story-deck presentation to product card lists

Adds StoryDeckView projection, IBuildDeckRepository.GetStoryDecksByClass interface method,
and BuildDeckRepository implementation that loads StoryDeckEntry rows for a class, fetches
matching BuildDeckProductEntry card lists, and expands each card by Number into a flat
CardIdArray. TDD: 2 tests in StoryDeckRepositoryTests (expand + empty-class).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SVSim.UnitTests/Repositories/StoryDeckRepositoryTests.cs

@@ -0,0 +1,66 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using SVSim.Database;
+using SVSim.Database.Enums;
+using SVSim.Database.Models;
+using SVSim.Database.Repositories.BuildDeck;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Repositories;
+
+public class StoryDeckRepositoryTests
+{
+    [Test]
+    public async Task GetStoryDecksByClass_returns_decks_with_expanded_card_arrays()
+    {
+        using var factory = new SVSimTestFactory();
+        using var scope = factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+
+        // FK: BuildDeckProducts requires a parent BuildDeckSeries row.
+        db.BuildDeckSeries.Add(new BuildDeckSeriesEntry { Id = 0 });
+        await db.SaveChangesAsync();
+
+        // Product 701 (class 1 build): 2x card 100, 1x card 200 = 3-card "deck".
+        db.BuildDeckProducts.Add(new BuildDeckProductEntry
+        {
+            Id = 701, SeriesId = 0, LeaderId = 1, DeckCode = "", ProductNameKey = "", IsEnabled = false,
+            Cards = new()
+            {
+                new BuildDeckProductCardEntry { CardId = 100, Number = 2, IsSpot = false },
+                new BuildDeckProductCardEntry { CardId = 200, Number = 1, IsSpot = false },
+            },
+        });
+        db.StoryDecks.Add(new StoryDeckEntry
+        {
+            DeckNo = 701, Kind = StoryDeckKind.Build, ClassId = 1, DeckName = "Pure Devotion",
+            SleeveId = 3000011, LeaderSkinId = 1, IsRecommend = 0, OrderNum = 0, EntryNo = 0, DeckFormat = null,
+        });
+        // A class-2 deck that must NOT be returned for class 1.
+        db.StoryDecks.Add(new StoryDeckEntry { DeckNo = 702, Kind = StoryDeckKind.Build, ClassId = 2, DeckName = "Other" });
+        await db.SaveChangesAsync();
+
+        var repo = new BuildDeckRepository(db);
+        var result = await repo.GetStoryDecksByClass(1);
+
+        Assert.That(result.Count, Is.EqualTo(1));
+        var deck = result[0];
+        Assert.That(deck.DeckNo, Is.EqualTo(701));
+        Assert.That(deck.DeckName, Is.EqualTo("Pure Devotion"));
+        Assert.That(deck.Kind, Is.EqualTo(StoryDeckKind.Build));
+        Assert.That(deck.CardIdArray.OrderBy(x => x), Is.EqualTo(new long[] { 100, 100, 200 }));
+    }
+
+    [Test]
+    public async Task GetStoryDecksByClass_returns_empty_for_class_with_no_decks()
+    {
+        using var factory = new SVSimTestFactory();
+        using var scope = factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+
+        var repo = new BuildDeckRepository(db);
+        var result = await repo.GetStoryDecksByClass(8);
+
+        Assert.That(result, Is.Empty);
+    }
+}