Phase 5.3-WSS (1/2): Core-WSS-Verbindungsklasse extrahiert

- Neu in PolyTrader.Core.Streaming: IBlockchainWssClient + AlchemyWssClient
  (+ Factory) und Modelle (BlockchainWssSubscription/LogSubscriptionFilter/
  BlockchainLogEvent). Domänen-agnostisch: Connect, eth_subscribe, Receive-Loop,
  Decode; Reconnect/Gating/Filter bleiben beim Aufrufer.
- AlchemyWebsocketService (weiter in App) nutzt jetzt den Core-Client via Factory:
  baut Filter aus getrackten Trader-Wallets, konsumiert OnLog, triggert Poll.
  ExecuteAsync-Reconnect/Backoff/Gating unverändert. Verhaltensneutral.
- Factory in DI registriert.
- Build 0 Fehler.

Naechster Teil: Modul-Listener (eigener Key+Filter) nach Modul-Umzug.

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

Program.cs

@@ -9,6 +9,7 @@ using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Options;
 using PolyTrader.Core.Configuration;
 using PolyTrader.Core.DependencyInjection;
+using PolyTrader.Core.Streaming;
 using PolyTraderSharp.Models;
 using PolyTraderSharp.Services;
 
@@ -35,6 +36,7 @@ internal static class Program
 					return client.GetDatabase(dbOptions.DatabaseName);
 				});
 				services.AddCorePersistence();
+				services.AddSingleton<IBlockchainWssClientFactory, AlchemyWssClientFactory>();
 				services.AddSingleton((IServiceProvider sp) => ServerSettings.Load("server_settings.xml"));
 				services.AddSingleton<TradingState>();
 				services.AddSingleton<CopyTradingState>();