feat(firewall-log): ulogd2 + NFLOG group 0 → JSON-Lines

Foundation für Live-Log + Firewall-History (Logsystem Phase 1):

- nft-Renderer: `log prefix "edgeguard:<rule-id>" group 0` für Rules
  mit log=true. Ohne `group` schrieb nft in kernel-log (dmesg), nie
  in netlink → ulogd2 sah nichts.
- ulogd2 + ulogd2-json als Depends, postinst legt /etc/ulogd.conf
  (NFLOG group 0 → /var/log/edgeguard/firewall.jsonl) + logrotate-
  Profil (14d, daily, copytruncate) + enable/restart ulogd2.service.
- /var/log/edgeguard/ ist root:edgeguard 0640 — ulogd2 schreibt
  (root), edgeguard-api liest (UI-Endpoints kommen in Phase 2).

End-to-End smoke-test bestätigt: ICMP echo → JSON-Line mit allen
Feldern (src_ip, dest_ip, oob.prefix, oob.in, icmp.*) in ~30ms.

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

packaging/debian/edgeguard-api/DEBIAN/control

@@ -12,7 +12,7 @@ Description: EdgeGuard — native Reverse-Proxy / LB / Forward-Proxy / VPN / Fir
  PG Streaming Replication + provider Floating-IP for HTTP ingress).
  .
  This package ships the management API, scheduler and CLI.
-Depends: postgresql-16 | postgresql-17, haproxy (>= 2.8), squid, wireguard-tools, unbound, chrony, nftables, certbot, openssl, sudo, adduser, systemd, ca-certificates
+Depends: postgresql-16 | postgresql-17, haproxy (>= 2.8), squid, wireguard-tools, unbound, chrony, nftables, certbot, openssl, sudo, adduser, systemd, ca-certificates, ulogd2, ulogd2-json
 Recommends: edgeguard-keydb (>= 6.3.4-edgeguard1), apparmor, fail2ban
 Section: admin
 Priority: optional