Phase 3c: Unkritische Call-Sites auf Repositories umgestellt

- MarketSyncService: markets-Zugriffe -> IMarketRepository (kein _db mehr).
- PolymarketWssClient: demo_positions -> IPositionRepository,
  accounts -> IAccountRepository (closed_trades bleibt vorerst auf _db,
  ClosedTrade-Repo folgt in Phase 5).
- Build 0 Fehler.

Hot-Path (CopyTradingEngine, TraderMonitorService) und frm_main-UI bewusst
noch NICHT migriert (Schritt B / Phase 5).

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

services/PolymarketWssClient.cs

@@ -1,5 +1,6 @@
 using System;
 using MongoDB.Driver;
+using PolyTrader.Core.Persistence;
 using PolyTraderSharp.Extensions;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
@@ -23,7 +24,9 @@ namespace PolyTraderSharp.Services
         private readonly PolymarketClobClient _clob;
         private readonly TerminalLogger _logger;
         private readonly IMongoDatabase _db;
-        
+        private readonly IPositionRepository _positionRepo;
+        private readonly IAccountRepository _accountRepo;
+
         // Tracking rate limits for auto redeem: max 2 attempts per position, 5 min apart
         private readonly ConcurrentDictionary<string, (int Count, DateTime LastAttempt)> _redeemAttempts = new();
 
@@ -32,13 +35,17 @@ namespace PolyTraderSharp.Services
             ServerSettings settings,
             PolymarketClobClient clob,
             TerminalLogger logger,
-            IMongoDatabase db)
+            IMongoDatabase db,
+            IPositionRepository positionRepo,
+            IAccountRepository accountRepo)
         {
             _state = state;
             _settings = settings;
             _clob = clob;
             _logger = logger;
             _db = db;
+            _positionRepo = positionRepo;
+            _accountRepo = accountRepo;
         }
 
         protected override async Task ExecuteAsync(CancellationToken stoppingToken)
@@ -248,7 +255,7 @@ namespace PolyTraderSharp.Services
             {
                 if (acc.OpenPositions.TryRemove(pos.TokenId, out _))
                 {
-                    _db.GetCollection<Position>($"demo_positions_{acc.AccountId}").Delete(pos.TokenId);
+                    _positionRepo.DeleteDemo(acc.AccountId, pos.TokenId);
 
                     decimal exactLimitPrice = acc.PreRedeemLimit;
                     decimal exitUsd = pos.Size * exactLimitPrice;
@@ -278,7 +285,7 @@ namespace PolyTraderSharp.Services
                     };
 
                     _db.GetCollection<ClosedTrade>("closed_trades").Insert(ct);
-                    _db.GetCollection<AccountState>("accounts").Upsert(acc);
+                    _accountRepo.Upsert(acc);
 
                     _logger.Trade($"✅ [AUTO REDEEM DEMO ERFOLGREICH] {pos.MarketQuestion} | Exit: {pos.Size:F2} @ {exactLimitPrice:F3} | PnL: ${realizedPnl:F2}");
                 }