feat(repo): IArenaTwoPickRewardRepository + tests

Adds GetRewardsByWinCountAsync and GetMaxWinCountAsync (short-circuits
to 0 on empty table). Registers as AddTransient in Program.cs alongside
other global catalog repos. 3 NUnit tests pass.

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

SVSim.Database/Repositories/Globals/IArenaTwoPickRewardRepository.cs

@@ -0,0 +1,9 @@
+using SVSim.Database.Models;
+
+namespace SVSim.Database.Repositories.Globals;
+
+public interface IArenaTwoPickRewardRepository
+{
+    Task<List<ArenaTwoPickReward>> GetRewardsByWinCountAsync(int winCount);
+    Task<int> GetMaxWinCountAsync();
+}