R8: Accounting- + Supervisor-Modul + Core-Datenfundament (S-0)

Portierung der beiden fehlenden Grundbausteine aus PolytraderSharp (voller Ausbau).

Core S-0 (Datenfundament fuer Analyse/Forensik):
- core_decision_journal + core_order_events (+ ReasonCode/Decision/OrderEvent-Enums),
  IDecisionJournal/IOrderEventLog mit fehlertoleranten EF-Impls (Handel bricht nie).
- SignalId-Durchreichung TradeSignal -> ExecutionService -> core_trade_history;
  ExecutionService schreibt an jeder Verzweigung Journal/Order-Events.
- JSONL-Log-Sink (LogJson + Dual-Sink), pure Analytik: RealizedPnlEngine (FIFO),
  TradeAnalytics, DossierBuilder. Migration AddAnalysisFoundation.

Accounting-Modul (acc_): unabhaengiger IBKR-Kontoauszug (Activity Flex Query) hinter
Interfaces mit Offline-Null-Stubs -> append-only Ledger + Periodenabrechnung/BWA + FX
(USD/EUR) + CSV/PDF (PDFsharp/MigraDoc). Steuerschicht bewusst offen (Platzhalter-Tab).
Kein Handel. Migration InitialAccounting.

Supervisor-Modul (sup_): read-only OpenRouter-Agent (Function-Calling-Loop) + read-only
Tool-Registry (8 Tools) + Profile + Dossier-Browser + Counterfactual-Job (Stub) +
Tagesbericht/MCP-Light (opt-in). Migration InitialSupervisor.

Verdrahtung: Program.cs (beide Module + Icons), slnx/App/Tests-Referenzen,
provision-db.ps1, AppSettings-Sektionen, docs/konzepte, README.

Tests: 79 -> 117 gruen (FIFO/KPIs/Dossier/JSONL, Classifier/Engine/FX/Idempotenz,
OpenRouter/Registry/Agent/MCP, STA-Konstruktion beider neuen Fenster).

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

tests/IBKRTrader.Tests/Modules/Accounting/FxConverterTests.cs

@@ -0,0 +1,39 @@
+using FluentAssertions;
+using IBKRTrader.Modules.Accounting.Logic;
+using IBKRTrader.Modules.Accounting.Models;
+
+namespace IBKRTrader.Tests.Modules.Accounting;
+
+[Trait("cat", "unit")]
+public class FxConverterTests
+{
+    private static FxRate R(int day, decimal rate) =>
+        new() { Date = new DateTime(2026, 5, day), UsdToEur = rate, Source = "ECB" };
+
+    [Fact]
+    public void UsesNearestRateOnOrBefore()
+    {
+        var conv = new FxConverter(new[] { R(1, 0.90m), R(10, 0.92m) });
+
+        conv.UsdToEurOn(new DateTime(2026, 5, 5)).Should().Be(0.90m);   // zwischen 1. und 10. → 0.90
+        conv.UsdToEurOn(new DateTime(2026, 5, 10)).Should().Be(0.92m);  // exakt
+        conv.UsdToEurOn(new DateTime(2026, 5, 20)).Should().Be(0.92m);  // nach letztem → letzter
+    }
+
+    [Fact]
+    public void ReturnsNull_WhenNoRateBeforeDate()
+    {
+        var conv = new FxConverter(new[] { R(10, 0.92m) });
+
+        conv.UsdToEurOn(new DateTime(2026, 5, 1)).Should().BeNull();
+        conv.UsdToEur(100m, new DateTime(2026, 5, 1)).Should().BeNull();
+    }
+
+    [Fact]
+    public void ConvertsAndRounds()
+    {
+        var conv = new FxConverter(new[] { R(1, 0.9123m) });
+
+        conv.UsdToEur(100m, new DateTime(2026, 5, 2)).Should().Be(91.23m);
+    }
+}