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

wwwroot/index.html

@@ -59,6 +59,7 @@
         <a id="dashboardAdminLink" class="dashboard-link" hidden>Benutzerverwaltung</a>
         <a id="dashboardApiKeysLink" class="dashboard-link" hidden>API-Keys</a>
         <a id="dashboardServerSettingsLink" class="dashboard-link" hidden>Servereinstellungen</a>
+        <a id="dashboardDbExplorerLink" class="dashboard-link" hidden>Datenbank</a>
         <a id="dashboardProfileLink" class="dashboard-link">Mein Profil</a>
       </div>
     </header>
@@ -533,6 +534,18 @@
   </div>
 </template>
 
+<template id="tpl-db-explorer">
+  <div class="page form-page">
+    <header>
+      <button class="back-btn icon-btn" data-page="dashboard"><i class="fa fa-arrow-left"></i></button>
+      <h1 id="dbExplorerTitle">Datenbank-Explorer</h1>
+    </header>
+    <div class="page-content">
+      <div id="dbExplorerContent"></div>
+    </div>
+  </div>
+</template>
+
 <template id="tpl-server-settings">
   <div class="page form-page">
     <header>
@@ -710,6 +723,7 @@
 <script src="js/pages/admin-page.js"></script>
 <script src="js/pages/api-keys-page.js"></script>
 <script src="js/pages/server-settings-page.js"></script>
+<script src="js/pages/db-explorer-page.js"></script>
 <script src="js/pages/shared-page.js"></script>
 <script src="js/app.js"></script>
 </body>