WireGuard access classes, firewall nftables fixes, network sync event refactor

- WireGuard: refactor to multi-interface 'access classes' model; extract config
  generation and helpers into lib/wireguard.py; add per-class up/down endpoints
  and API routes; update UI with class management pages and QR code component
- Firewall: fix zone creation with --new-zone before --set-target; skip
  masquerade on public zone; add masquerade propagation for nftables backend
  so NAT works when internal zones exit via public
- Network: rename sync event subsystem 'network' -> 'networkd'; always stamp
  config hash even when deployment fails (fixes pending-changes detection)
- DHCP: add new API endpoint and update frontend page
- State/Sync: update state collectors and sync buses for new subsystems
- Docs: update API and config documentation for new endpoints and schemas

webui/static/hoover/index.js

@@ -48,3 +48,6 @@ export { ApplyConfirm } from './components/applyconfirm.js?v=9';
 
 /* ── UI Components: Toast ────────────────────────────────────── */
 export { ToastContainer } from './components/toast.js?v=9';
+
+/* ── UI Components: QR Code ──────────────────────────────────── */
+export { qrSVG, QRCodeVNode, LogoUpload } from './components/qr.js?v=9';