feat(packs): PackDrawTable aggregate + IPackDrawTableRepository

Aggregate (Config + SlotRates + CardWeights) and a single-pack getter
loaded as one unit per /pack/open. PackOpenService consumes the
aggregate; tests use the production seed (fixture overlay) to validate
shape.

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

SVSim.Database/Repositories/PackDrawTable/PackDrawTable.cs

@@ -0,0 +1,14 @@
+using SVSim.Database.Models;
+
+namespace SVSim.Database.Repositories.PackDrawTables;
+
+/// <summary>
+/// All draw data for a single pack: per-pack config + slot rates + per-card weights.
+/// Loaded as one unit by <see cref="IPackDrawTableRepository.GetAsync"/>.
+/// </summary>
+public sealed class PackDrawTable
+{
+    public required PackDrawConfigEntry Config { get; init; }
+    public required IReadOnlyList<PackDrawSlotRateEntry> SlotRates { get; init; }
+    public required IReadOnlyList<PackDrawCardWeightEntry> CardWeights { get; init; }
+}