feat: nettoyage menu + suppression modules inexistants + log viewer

- Sidebar : retrait des liens files, logs, services (non implémentés)
- Migration 001 : suppression des inserts files/logs/services
- Migration 002 : DELETE des modules inexistants en DB existante
- logbuffer : ring buffer mémoire branché sur log.SetOutput
- GET /api/settings/logs : retourne les 300 dernières lignes de log
- Settings : onglet Logs avec auto-refresh (5s/10s/30s/60s/désactivé, défaut 10s)

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

frontend/src/locales/en.json

@@ -118,7 +118,11 @@
     "sidebarPosition": "Sidebar position",
     "left": "Left",
     "right": "Right",
-    "noAuditLog": "No audit log entries"
+    "noAuditLog": "No audit log entries",
+    "logs": "Logs",
+    "logsRefresh": "Auto-refresh",
+    "logsNoRefresh": "Disabled",
+    "noLogs": "No logs available"
   },
   "modules": {
     "desc": "Manage installed modules on ProxmoxPanel.",