fix: consolidate WireGuard port config and propagate port changes to UI

- docker-compose: fix WireGuard port mapping to ${WG_PORT}:${WG_PORT} so
  the daemon ListenPort matches the Docker host-to-container binding
- app.py: sync wireguard.port ↔ identity.wireguard_port in both directions
  so changing either keeps them consistent; identity path now also updates
  wg0.conf via wireguard_manager.update_config
- Settings.jsx: remove duplicate wireguard_port from Cell Identity section
  (port is configurable under WireGuard VPN service config); add
  refreshConfig() after saveService so other pages see new values immediately
- WireGuard.jsx: import useConfig() and use service_configs.wireguard.port
  as the reactive port source for endpoint display and port-open warnings

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

docker-compose.yml

@@ -167,7 +167,7 @@ services:
       - PUID=${PUID:-1000}
       - PGID=${PGID:-1000}
     ports:
-      - "${WG_PORT:-51820}:51820/udp"
+      - "${WG_PORT:-51820}:${WG_PORT:-51820}/udp"
     volumes:
       - ./config/wireguard:/config
       - /lib/modules:/lib/modules