Phase 7: Testprojekt (xUnit) + Repository-Tests

- Neues Projekt tests/PolyTrader.Tests (xUnit, EF Core InMemory-Provider),
  zur Solution hinzugefügt.
- InMemoryContextFactory<TContext>: Test-IDbContextFactory (isolierte In-Memory-DB
  je Test, geteilt über alle Kontexte einer Factory – wie im echten Betrieb).
- 18 Tests über die EF-Repos:
  - TrackedTrader: Upsert insert/update ohne Duplikat, Delete,
    AssignedAccountIds-JSON-Round-Trip (Value-Converter) + Set-Ersetzung.
  - CopyTradingAccountSettings: Upsert/Get (Dezimalwerte), Get-null, Delete.
  - CopyTradeLog: Insert/Find, Exists-Dedup (Account+Token), Predikat-Filter.
  - MasterTraderHistory: Exists-Zeitfenster, GetByTraderSince-Cutoff.
  - Core Accounts: Upsert insert/update, Delete.
- Alle 18 grün.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/PolyTrader.Tests/AccountSettingsRepositoryTests.cs

@@ -0,0 +1,61 @@
+using PolyTrader.Modules.CopyTrading.Persistence.Ef;
+using PolyTrader.Tests.TestSupport;
+using PolyTraderSharp.Models;
+using Xunit;
+
+namespace PolyTrader.Tests
+{
+    public class AccountSettingsRepositoryTests
+    {
+        private static EfCopyTradingAccountSettingsRepository NewRepo() =>
+            new(new InMemoryContextFactory<CopyTradingDbContext>(o => new CopyTradingDbContext(o)));
+
+        [Fact]
+        public void Upsert_and_Get_persists_decimal_values()
+        {
+            var repo = NewRepo();
+            repo.Upsert(new CopyTradingAccountSettings
+            {
+                AccountId = 1,
+                PerMarketLimit = 0.5m,
+                PerMasterLimit = 15m,
+                MaxBuyPrice = 98m,
+                PreRedeemLimit = 99.5m
+            });
+
+            var s = repo.Get(1);
+            Assert.NotNull(s);
+            Assert.Equal(0.5m, s!.PerMarketLimit);
+            Assert.Equal(15m, s.PerMasterLimit);
+            Assert.Equal(98m, s.MaxBuyPrice);
+            Assert.Equal(99.5m, s.PreRedeemLimit);
+        }
+
+        [Fact]
+        public void Get_returns_null_when_missing()
+        {
+            var repo = NewRepo();
+            Assert.Null(repo.Get(42));
+        }
+
+        [Fact]
+        public void Upsert_updates_existing_without_duplicating()
+        {
+            var repo = NewRepo();
+            repo.Upsert(new CopyTradingAccountSettings { AccountId = 1, PerMarketLimit = 1m });
+            repo.Upsert(new CopyTradingAccountSettings { AccountId = 1, PerMarketLimit = 2m });
+
+            Assert.Single(repo.GetAll());
+            Assert.Equal(2m, repo.Get(1)!.PerMarketLimit);
+        }
+
+        [Fact]
+        public void Delete_removes_settings()
+        {
+            var repo = NewRepo();
+            repo.Upsert(new CopyTradingAccountSettings { AccountId = 1 });
+            repo.Delete(1);
+            Assert.Empty(repo.GetAll());
+        }
+    }
+}