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/ToolService.cs

@@ -10,7 +10,6 @@ using System.Text.Json;
 using System.Text.RegularExpressions;
 using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.FileSystemGlobbing;
 using Microsoft.Extensions.FileSystemGlobbing.Abstractions;
 
@@ -18,12 +17,12 @@ namespace Gott.Services;
 
 public class ToolService
 {
-    private readonly IConfiguration _config;
+    private readonly ServerSettingsService _settings;
     private IHttpClientFactory _httpFactory;
 
-    public ToolService(IConfiguration config)
+    public ToolService(ServerSettingsService settings)
     {
-        _config = config;
+        _settings = settings;
     }
 
     public void SetHttpClientFactory(IHttpClientFactory httpFactory)
@@ -31,9 +30,9 @@ public class ToolService
         _httpFactory = httpFactory;
     }
 
-    private int ExecuteTimeoutSeconds => _config.GetValue<int>("ExecuteTimeout", 180);
-    public bool HasGitHubToken => !string.IsNullOrWhiteSpace(_config["GitHubToken"]);
-    public bool HasSerperKey => !string.IsNullOrWhiteSpace(_config["SerperApiKey"]);
+    private int ExecuteTimeoutSeconds => _settings.GetInt("ExecuteTimeout", 180);
+    public bool HasGitHubToken => !string.IsNullOrWhiteSpace(_settings.Get("GitHubToken"));
+    public bool HasSerperKey => !string.IsNullOrWhiteSpace(_settings.Get("SerperApiKey"));
     public const string AskUserChoiceToolName = "ask_user_choice";
 
     /// <summary>
@@ -858,7 +857,7 @@ public class ToolService
 
     private async Task<string> ExecuteGitHubCodeSearch(JsonElement input, CancellationToken ct)
     {
-        var token = _config["GitHubToken"] ?? "";
+        var token = _settings.Get("GitHubToken");
         if (string.IsNullOrWhiteSpace(token))
             return "Fehler: Kein GitHubToken konfiguriert. Bitte in den Server-Einstellungen hinterlegen.";
 
@@ -961,7 +960,7 @@ public class ToolService
 
     private async Task<string> ExecuteSerperWebSearch(JsonElement input, CancellationToken ct)
     {
-        var apiKey = _config["SerperApiKey"] ?? "";
+        var apiKey = _settings.Get("SerperApiKey");
         if (string.IsNullOrWhiteSpace(apiKey))
             return "Fehler: Kein SerperApiKey konfiguriert. Bitte in den Server-Einstellungen hinterlegen.";