Prebuilt deck purchasing and fixes

SVSim.Database/Repositories/BuildDeck/IBuildDeckRepository.cs

@@ -0,0 +1,29 @@
+using SVSim.Database.Models;
+
+namespace SVSim.Database.Repositories.BuildDeck;
+
+public interface IBuildDeckRepository
+{
+    /// <summary>
+    /// Load enabled series (filtered by addSeriesId when non-zero) with all owned children
+    /// for /build_deck/info. Series and per-series products are sorted by OrderIndex desc.
+    /// </summary>
+    Task<List<BuildDeckSeriesEntry>> GetEnabledCatalog(int addSeriesId);
+
+    /// <summary>
+    /// Load a single product (with Series + Cards + Rewards + Series.SeriesRewards) by id.
+    /// Returns null if absent. Used by /build_deck/buy and /build_deck/get_purchase_count.
+    /// </summary>
+    Task<BuildDeckProductEntry?> GetProduct(int productId);
+
+    /// <summary>
+    /// Per-viewer purchase counter snapshot. Key = product_id.
+    /// </summary>
+    Task<Dictionary<int, ViewerBuildDeckProductPurchase>> GetPurchasesForViewer(long viewerId);
+
+    /// <summary>
+    /// Increment the (ViewerId, ProductId) purchase counter by 1 (insert if absent).
+    /// Returns the new total.
+    /// </summary>
+    Task<int> IncrementPurchaseCount(long viewerId, int productId);
+}