feat(backup): Restore-Pfad — POST /backups/:id/restore + UI

backup.Service.Restore(id) schreibt /var/lib/edgeguard/restore.sh
und dispatcht via `sudo systemd-run --unit=edgeguard-restore.service`.
Skript-Ablauf:
  1. tar -xzf der Backup-Datei → /var/lib/edgeguard/restore-tmp
  2. state-files (setup.json/license/jwt/node.conf/acme-account) per
     cp -a zurück, chown edgeguard
  3. systemctl stop edgeguard-api + scheduler (DB-Connections freigeben)
  4. sudo -u postgres psql -f dump.sql (--clean droppt + recreated)
  5. edgeguard-ctl render-config (haproxy/nft/squid/unbound/chrony)
  6. systemctl start edgeguard-api + scheduler
  7. rm -rf restore-tmp + restore.sh

UI: pro Backup-Row neuer Restore-Button mit Popconfirm. Beim Trigger
zeigt sich das vertraute Fullscreen-Overlay (Klassen .update-modal*
re-used) mit 4 Steps (Extract / DB-Restore / Render / Restart) + Live-
Timer. Health-Poll alle 3s detektiert API-Restart + reload. Safety-
Timeout 3 min für große DB-Dumps.

postinst: sudoers für `systemd-run --unit=edgeguard-restore.service
--description=... --collect bash /var/lib/edgeguard/restore.sh` +
zugehöriges `systemctl reset-failed`. Pfad fix damit kein Wildcard
nötig wird.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

management-ui/src/i18n/locales/en/common.json

@@ -632,6 +632,20 @@
     "failed": "Backup failed",
     "deleted": "Backup deleted",
     "download": "Download",
+    "restore": "Restore",
+    "restoreOk": "Start restore",
+    "restoreDone": "Restore complete — page reloading.",
+    "restoreFailed": "Restore failed",
+    "restoreRunning": "Restore in progress …",
+    "restoreHint": "edgeguard-api will restart; the UI reloads after the restart.",
+    "confirmRestoreTitle": "Restore this backup?",
+    "confirmRestoreDesc": "Database content will be replaced with {{file}} + state files. edgeguard-api + scheduler will restart. Changes made since the backup are lost.",
+    "step": {
+      "extract": "Extract tar",
+      "psql": "DB restore (psql)",
+      "render": "Re-render configs",
+      "restart": "Restart services"
+    },
     "downloadTooltip": "Download tar.gz",
     "refreshTooltip": "Reload list",
     "confirmDelete": "Really delete backup {{file}}?",