fix: resolve all quality gate failures — i18n key, typography tokens, PHPStan errors, style

- Add missing i18n key "LDAP attribute map could not be encoded" (de+en)
- Replace raw font-weight/line-height with design tokens in app-topbar.css
- Fix import ordering in SchedulerRunService.php (php-cs-fixer)
- Fix PHPStan mock chain errors in DebitorDetailServiceTest and TenantSsoServiceTest (PHPUnit 12 API)
- Simplify redundant comparison in NotificationService dedupe window
- Add PHPStan type hint for mock callback array in SchedulerJobFailedNotificationListenerTest
- Fix undefined variable and add flow-analysis suppression in login().php
- Increase dev PHP memory_limit to 1G for PHPStan (prod stays 256M)

All 6 quality gates now pass: QG-001 (1618 tests), QG-002 (0 errors),
QG-003 (6630 assertions), QG-006 (0 fixable), QG-008, QG-009.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

i18n/default_de.json

@@ -1434,6 +1434,7 @@
   "Write-only. Leave empty to keep current value.": "Nur Schreibzugriff. Leer lassen, um den aktuellen Wert beizubehalten.",
   "Your account is deactivated.": "Ihr Konto ist deaktiviert.",
   "LDAP": "LDAP",
+  "LDAP attribute map could not be encoded": "LDAP-Attributzuordnung konnte nicht kodiert werden",
   "Drop file here or click to select": "Datei hierher ziehen oder klicken",
   "Remove selected file": "Ausgewaehlte Datei entfernen",
   "Replace": "Ersetzen",