Add compliance audit log

Immutable audit_log table in the scanner DB records every significant
admin action (profile save/delete, token create/revoke, PIN changes,
source add/update/delete, scheduler job changes, scan start/stop, SMTP
save, dispositions, item delete/redact). GET /api/audit_log exposes
entries newest-first. New Audit Log tab in the Settings modal renders
the table on demand. Settings modal widened 540→640 px and tab labels
set to white-space:nowrap so the six-tab row fits on one line.

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

lang/de.json

@@ -675,6 +675,14 @@
   "m365_settings_tab_general": "Allgemein",
   "m365_settings_tab_email": "E-Mail-Bericht",
   "m365_settings_tab_database": "Datenbank",
+  "m365_settings_tab_auditlog": "Prüfprotokoll",
+  "m365_audit_title": "Compliance-Prüfprotokoll",
+  "m365_audit_col_time": "Zeitpunkt",
+  "m365_audit_col_action": "Aktion",
+  "m365_audit_col_detail": "Detail",
+  "m365_audit_col_ip": "IP",
+  "m365_audit_loading": "Wird geladen…",
+  "m365_audit_empty": "Noch keine Prüfereignisse aufgezeichnet.",
   "m365_settings_appearance": "Erscheinungsbild",
   "m365_settings_language": "Sprache",
   "m365_settings_theme": "Design",