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

Endpoints/ServerSettingsEndpoint.cs

@@ -86,6 +86,23 @@ public static class ServerSettingsEndpoint
                 case "bool":
                     settings.SetBool(def.Key, prop.ValueKind == JsonValueKind.True);
                     break;
+                case "string_array":
+                    if (prop.ValueKind == JsonValueKind.Array)
+                    {
+                        var arr = new List<string>();
+                        foreach (var el in prop.EnumerateArray())
+                        {
+                            var s = el.GetString();
+                            if (!string.IsNullOrWhiteSpace(s)) arr.Add(s);
+                        }
+                        settings.SetStringArray(def.Key, arr.ToArray());
+                    }
+                    else if (prop.ValueKind == JsonValueKind.String)
+                    {
+                        // Fallback: CSV-String
+                        settings.Set(def.Key, prop.GetString() ?? "");
+                    }
+                    break;
             }
         }