Refactor: Server-Settings von appsettings.json in DB-Tabelle (server_settings)

- Neuer ServerSettingsService: zentrale Settings in SQLite mit In-Memory-Cache
- Auto-Migration: bestehende appsettings.Production.json wird einmalig in DB übernommen
- Alle Services umgestellt: IConfiguration → ServerSettingsService (dynamisch, kein Neustart)
- Port bleibt als einziges Setting in appsettings.Production.json (erfordert Neustart)
- ServerSettingsEndpoint: liest/schreibt DB statt JSON-Datei, Port als Sonder-Setting
- IConfiguration komplett entfernt aus allen Services (ChatService, ToolService, AnthropicService,
  OpenAiService, KreaService, TelegramService, KeyScannerService, GitHubEventScannerService)
- AuthMiddleware: KreaApiKey dynamisch aus DB
- appsettings.json bereinigt: nur noch Port und Logging
- Dokumentation aktualisiert (ARCHITECTURE.md, ARCHITECTURE_QUICK.md, README.md)

Services/TelegramService.cs

@@ -15,20 +15,20 @@ public class TelegramService
     private readonly DatabaseService _db;
     private readonly ChatService _chatService;
     private readonly AnthropicService _anthropic;
-    private readonly int _maxIterations;
+    private readonly ServerSettingsService _settings;
 
     public TelegramService(
         IHttpClientFactory httpFactory,
         DatabaseService db,
         ChatService chatService,
         AnthropicService anthropic,
-        int maxIterations = 100)
+        ServerSettingsService settings)
     {
         _httpFactory = httpFactory;
         _db = db;
         _chatService = chatService;
         _anthropic = anthropic;
-        _maxIterations = maxIterations;
+        _settings = settings;
     }
 
     // ── Webhook-Update verarbeiten ──
@@ -161,7 +161,7 @@ public class TelegramService
 
     private async Task HandleMessage(long chatId, string userText, string botToken, string botUserId, SessionRecord session)
     {
-        var ctx = await _chatService.PrepareContext(session.SessionId, botUserId, _maxIterations);
+        var ctx = await _chatService.PrepareContext(session.SessionId, botUserId, _settings.GetInt("MaxIterations", 100));
         if (ctx == null)
         {
             await SendMessage(chatId, botToken, "❌ Kein Agent konfiguriert. Bitte weise der Session im Web-UI einen Agent zu.");