feat: add Services and Logs modules (systemctl + journalctl via SSH)

Backend:
- modules/services: list, status, start/stop/restart systemctl services
  with pct exec support for LXC targets
- modules/logs: journalctl unit listing + WebSocket live streaming
  (direct SSH connection, journalctl -f, graceful teardown on WS close)
- migrations/003: seed services and logs modules in DB
- main.go: register services.New() and logs.New() in module loader

Frontend:
- services.html: target selector, search/filter, services table with
  active state indicators and start/stop/restart buttons
- logs.html: target + unit selectors, live follow toggle, scrollable
  terminal output with 3000-line cap
- app.js: servicePage() and logsPage() Alpine components + navItems
- locales: services and logs i18n keys (fr + en)
- pages.css: services table, state dots, logs output styles

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

frontend/locales/fr.json

@@ -115,6 +115,34 @@
     "desc": "Navigateur de fichiers SFTP",
     "moduleNotEnabled": "Module non activé. Rendez-vous dans Paramètres → Modules pour l'activer."
   },
+  "services": {
+    "desc": "Gestion des services systemd",
+    "target": "Cible",
+    "filter": "Filtrer par nom ou description…",
+    "noServices": "Aucun service trouvé",
+    "name": "Service",
+    "status": "Statut",
+    "substate": "Sous-état",
+    "description": "Description",
+    "start": "Démarrer",
+    "stop": "Arrêter",
+    "restart": "Redémarrer",
+    "reload": "Recharger",
+    "enable": "Activer",
+    "disable": "Désactiver"
+  },
+  "logs": {
+    "desc": "Consultation des journaux système via journalctl",
+    "target": "Cible",
+    "unit": "Unité",
+    "unitAll": "Toutes les unités",
+    "lines": "Lignes",
+    "follow": "Suivre en temps réel",
+    "stopFollow": "Arrêter",
+    "clear": "Effacer",
+    "noLogs": "Aucun journal — cliquez sur « Suivre » pour démarrer",
+    "connecting": "Connexion en cours…"
+  },
   "settings": {
     "general": "Général",
     "infrastructure": "Infrastructure",