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>

internal/services/backup/backup.go

@@ -468,6 +468,102 @@ FROM backups WHERE id = $1`, id).Scan(
 	return &e, filepath.Join(s.BackupDir, e.File), nil
 }
 
+// Restore startet einen full-system-restore aus einem vorhandenen
+// Backup-Tarball. Läuft analog `/system/upgrade`-Pattern: wir
+// schreiben /var/lib/edgeguard/restore.sh und dispatchen es per
+// `sudo systemd-run --unit=edgeguard-restore.service`. Das Skript
+// stoppt edgeguard-api+scheduler, kopiert die files/, restored den
+// DB-Dump als postgres, re-rendert die Configs und startet die
+// Services neu.
+//
+// Returnt sofort nach dem Dispatch (asynchron) — der eigentliche
+// Restore läuft im Hintergrund. UI pollt /healthz für die
+// Version-Flip-Detection (analog Upgrade).
+func (s *Service) Restore(ctx context.Context, id int64) (*Entry, error) {
+	e, path, err := s.Get(ctx, id)
+	if err != nil {
+		return nil, fmt.Errorf("backup not found: %w", err)
+	}
+	if e.Status != "success" {
+		return nil, fmt.Errorf("backup is in status %q — cannot restore", e.Status)
+	}
+	if _, err := os.Stat(path); err != nil {
+		return nil, fmt.Errorf("backup file missing on disk: %w", err)
+	}
+
+	const scriptPath = "/var/lib/edgeguard/restore.sh"
+	script := fmt.Sprintf(`#!/bin/bash
+# Generated by edgeguard-api — restore from %s
+set -e
+sleep 2  # let API return 202 first
+TARBALL=%q
+TMP=/var/lib/edgeguard/restore-tmp
+echo "[restore] extract $TARBALL → $TMP"
+rm -rf "$TMP"
+mkdir -p "$TMP"
+tar -xzf "$TARBALL" -C "$TMP"
+
+# 1) Restore node-local state files BEFORE the DB swap so a crash
+#    mid-restore leaves the box in a state where the next API-start
+#    sees the new keys/setup. DB will be partial but recoverable.
+echo "[restore] state files"
+for f in setup.json license_key license.cache trial.json .jwt_fingerprint node.conf; do
+    if [ -f "$TMP/files/$f" ]; then
+        cp -a "$TMP/files/$f" /var/lib/edgeguard/
+    fi
+done
+if [ -d "$TMP/files/acme-account" ]; then
+    mkdir -p /var/lib/edgeguard/acme-account
+    cp -a "$TMP/files/acme-account/." /var/lib/edgeguard/acme-account/
+fi
+chown -R edgeguard:edgeguard /var/lib/edgeguard/setup.json \
+    /var/lib/edgeguard/license_key /var/lib/edgeguard/license.cache \
+    /var/lib/edgeguard/trial.json /var/lib/edgeguard/.jwt_fingerprint \
+    /var/lib/edgeguard/node.conf /var/lib/edgeguard/acme-account 2>/dev/null || true
+
+# 2) Stop API+scheduler so psql can DROP/CREATE tables without active
+#    connections fighting the dump-restore.
+echo "[restore] stop services"
+systemctl stop edgeguard-api edgeguard-scheduler
+
+# 3) Apply DB dump. pg_dump --clean emits DROP TABLE IF EXISTS so
+#    we don't need to wipe the schema manually.
+echo "[restore] psql -f dump.sql"
+sudo -u postgres /usr/bin/psql --quiet -d edgeguard -f "$TMP/dump.sql"
+
+# 4) Re-render configs from the freshly restored DB. Each renderer
+#    triggers its own service reload — haproxy, nft, etc. so the
+#    user-visible state matches DB-state immediately.
+echo "[restore] render-config"
+sudo -u edgeguard /usr/bin/edgeguard-ctl render-config || true
+
+# 5) Restart edgeguard-api so the UI's /healthz poll sees version-
+#    flip / fresh connection. Scheduler comes back automatically.
+echo "[restore] start services"
+systemctl start edgeguard-api edgeguard-scheduler
+
+rm -rf "$TMP" "$0"
+echo "[restore] complete"
+`, e.File, path)
+
+	if err := os.WriteFile(scriptPath, []byte(script), 0o755); err != nil {
+		return nil, fmt.Errorf("write %s: %w", scriptPath, err)
+	}
+
+	const unitName = "edgeguard-restore.service"
+	_ = exec.Command("sudo", "-n", "/usr/bin/systemctl",
+		"reset-failed", unitName).Run()
+	cmd := exec.Command("sudo", "-n", "/usr/bin/systemd-run",
+		"--unit="+unitName,
+		"--description=EdgeGuard self-restore",
+		"--collect",
+		"bash", scriptPath)
+	if err := cmd.Run(); err != nil {
+		return nil, fmt.Errorf("systemd-run: %w", err)
+	}
+	return e, nil
+}
+
 // Delete entfernt File + DB-Row.
 func (s *Service) Delete(ctx context.Context, id int64) error {
 	_, path, err := s.Get(ctx, id)