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/css/form.css

@@ -730,3 +730,156 @@ a.admin-user-meta {
   text-align: right;
   flex-shrink: 0;
 }
+
+/* ── Checkbox Group (string_array Settings) ── */
+
+.checkbox-group {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 6px;
+}
+
+.checkbox-group-actions {
+  width: 100%;
+  display: flex;
+  gap: 6px;
+  margin-bottom: 2px;
+}
+
+.checkbox-group-actions .btn-xs {
+  padding: 2px 8px;
+  font-size: 0.75em;
+  border-radius: var(--border-radius);
+  cursor: pointer;
+}
+
+.checkbox-item {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  padding: 4px 8px;
+  border: 1px solid var(--f1-border);
+  border-radius: var(--border-radius);
+  cursor: pointer;
+  font-size: 0.85em;
+  background: color-mix(in srgb, var(--f1-bg) 25%, transparent);
+  transition: border-color 0.15s, background 0.15s;
+  user-select: none;
+}
+
+.checkbox-item:hover {
+  border-color: var(--accent);
+}
+
+.checkbox-item:has(input:checked) {
+  border-color: var(--accent);
+  background: color-mix(in srgb, var(--accent) 15%, transparent);
+}
+
+.checkbox-item input[type="checkbox"] {
+  width: 14px;
+  height: 14px;
+  accent-color: var(--accent);
+  cursor: pointer;
+  margin: 0;
+}
+
+/* ── Database Explorer ── */
+
+.db-table {
+  width: 100%;
+  border-collapse: collapse;
+  font-size: .9em;
+}
+
+.db-table th,
+.db-table td {
+  padding: 8px 12px;
+  text-align: left;
+  border-bottom: 1px solid var(--border);
+}
+
+.db-table th {
+  background: var(--bg-secondary);
+  font-weight: 600;
+  position: sticky;
+  top: 0;
+  z-index: 1;
+  white-space: nowrap;
+}
+
+.db-table tbody tr:hover {
+  background: color-mix(in srgb, var(--accent) 8%, transparent);
+}
+
+.db-table-row.clickable {
+  cursor: pointer;
+}
+
+.db-table-row.clickable:hover .db-table-name {
+  color: var(--accent);
+}
+
+.db-table-name {
+  font-weight: 500;
+}
+
+.db-table-name i {
+  margin-right: 6px;
+  opacity: .5;
+}
+
+.db-table-num {
+  text-align: right !important;
+  font-variant-numeric: tabular-nums;
+  opacity: .7;
+}
+
+.db-table-wrapper {
+  overflow-x: auto;
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+}
+
+.db-data-table td {
+  max-width: 300px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  font-family: var(--font-mono, monospace);
+  font-size: .85em;
+}
+
+.db-null {
+  opacity: .3;
+  font-style: italic;
+}
+
+.db-info-bar {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  padding: 8px 0;
+  font-size: .9em;
+  opacity: .7;
+}
+
+.db-pagination {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.db-page-info {
+  font-size: .85em;
+}
+
+.db-back-link {
+  opacity: .6;
+  transition: opacity .15s;
+}
+
+.db-back-link:hover {
+  opacity: 1;
+  color: var(--accent);
+}