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)

Middleware/AuthMiddleware.cs

@@ -1,19 +1,18 @@
 using System.Threading.Tasks;
 using Gott.Services;
 using Microsoft.AspNetCore.Http;
-using Microsoft.Extensions.Configuration;
 
 namespace Gott.Middleware;
 
 public class AuthMiddleware
 {
     private readonly RequestDelegate _next;
-    private readonly string _kreaApiKey;
+    private readonly ServerSettingsService _settings;
 
-    public AuthMiddleware(RequestDelegate next, IConfiguration config)
+    public AuthMiddleware(RequestDelegate next, ServerSettingsService settings)
     {
         _next = next;
-        _kreaApiKey = config["KreaApiKey"] ?? "";
+        _settings = settings;
     }
 
     public async Task InvokeAsync(HttpContext ctx, AuthService auth, DatabaseService db)
@@ -34,10 +33,11 @@ public class AuthMiddleware
         }
 
         // Krea API-Key auth (for automation without user context)
-        if (path.StartsWith("/api/images/") && !string.IsNullOrEmpty(_kreaApiKey))
+        var kreaApiKey = _settings.Get("KreaApiKey");
+        if (path.StartsWith("/api/images/") && !string.IsNullOrEmpty(kreaApiKey))
         {
             var apiKey = ctx.Request.Headers["X-Api-Key"].ToString();
-            if (!string.IsNullOrEmpty(apiKey) && apiKey == _kreaApiKey)
+            if (!string.IsNullOrEmpty(apiKey) && apiKey == kreaApiKey)
             {
                 await _next(ctx);
                 return;