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/OpenAiService.cs

@@ -156,17 +156,20 @@ public class OpenAiService
     private List<ProviderModel> _openaiModels       = new List<ProviderModel>();
     private readonly string _cacheFile;
 
-    public OpenAiService(IHttpClientFactory httpFactory, DatabaseService db, ToolService toolService, Microsoft.Extensions.Configuration.IConfiguration configuration, string dataDir)
+    private readonly ServerSettingsService _settings;
+
+    public OpenAiService(IHttpClientFactory httpFactory, DatabaseService db, ToolService toolService, ServerSettingsService settings, string dataDir)
     {
         _httpFactory = httpFactory;
         _db = db;
         _toolService = toolService;
+        _settings = settings;
         _cacheFile = Path.Combine(dataDir, "models_cache.json");
         Providers = new Dictionary<string, (string BaseUrl, string ApiKey)>
         {
             ["nvidia"]       = ("https://g4f.space/api/nvidia/v1",                                    ""),
             ["pollinations"] = ("https://text.pollinations.ai/openai",                                ""),
-            ["gemini"]       = ("https://generativelanguage.googleapis.com/v1beta/openai", configuration["GeminiApiKey"] ?? ""),
+            ["gemini"]       = ("https://generativelanguage.googleapis.com/v1beta/openai",            ""),  // Key kommt dynamisch aus Settings
             ["openai"]       = ("https://api.openai.com/v1",                                          "")  // Key kommt dynamisch aus DB
         };
     }
@@ -209,7 +212,7 @@ public class OpenAiService
         _nvidiaModels       = await FetchModels("https://g4f.space/api/nvidia/models", "Nvidia");
         _pollinationsModels = await FetchModels("https://text.pollinations.ai/models", "Pollinations");
 
-        var geminiApiKey = Providers["gemini"].ApiKey;
+        var geminiApiKey = _settings.Get("GeminiApiKey");
         if (!string.IsNullOrEmpty(geminiApiKey))
             _geminiModels = await FetchModels("https://generativelanguage.googleapis.com/v1beta/openai/models", "Gemini", geminiApiKey);
         else
@@ -363,6 +366,10 @@ public class OpenAiService
         if (!string.IsNullOrEmpty(apiKeyOverride))
             providerConfig = (providerConfig.BaseUrl, apiKeyOverride);
 
+        // Gemini: Key dynamisch aus ServerSettings holen (falls nicht per Override gesetzt)
+        if (provider == "gemini" && string.IsNullOrEmpty(providerConfig.ApiKey))
+            providerConfig = (providerConfig.BaseUrl, _settings.Get("GeminiApiKey"));
+
         try
         {
             // OpenAI-kompatibles Messages-Format aufbauen