Fix Caddy routing and add caddy_net to all Docker services

- lib/common.sh: fix broken reverse_proxy target — localhost inside Caddy's
  container is the container's own loopback, not the host; change to
  host.docker.internal so proxied ports are actually reachable
- services/caddy.sh: add extra_hosts host.docker.internal:host-gateway so
  the above resolves correctly; create caddy_net bridge network in Caddy's
  own compose so other services can reference it as external; update all
  Caddyfile template comments and README examples to match
- services/filebrowser.sh: update image tag from deprecated :s6 to :latest;
  remove non-functional PUID/PGID env vars (filebrowser/filebrowser does not
  honour them); add configure_caddy_for_service call; add caddy_net
- services/ntfy.sh: add configure_caddy_for_service call; add caddy_net
- services/portainer.sh: add configure_caddy_for_service call; add caddy_net
- services/frigate-notify.sh, watchtower.sh: add caddy_net for
  container-to-container comms (frigate, ntfy) without a Caddy call
- All remaining web-facing Docker services: add caddy_net network block to
  docker-compose and CADDY_NET to .env where applicable; services using
  network_mode: host (wolf-pair, lyrion) have the top-level block only

https://claude.ai/code/session_01UZus2Q9gNTfUdqSMrhuX29

services/frigate-audio.sh

@@ -169,6 +169,7 @@ FN_FRIGATE__MQTT__PASSWORD=${MQTT_PASS}
 FN_FRIGATE__SERVER=http://frigate:5000
 FN_FRIGATE__PUBLIC_URL=${FRIGATE_PUBLIC_URL}
 FN_ALERTS__NTFY__SERVER=${NTFY_SERVER}
+CADDY_NET=$SITE_CADDY_NET
 ENVEOF
     chmod 600 "$DIR/.env"
     log_success ".env written"
@@ -225,6 +226,8 @@ COMPOSEEOF
       - "8554:8554"
       - "8555:8555/tcp"
       - "8555:8555/udp"
+    networks:
+      - caddy_net
     healthcheck:
       test: ["CMD", "curl", "-f", "http://127.0.0.1:5000/api/version"]
       interval: 10s
@@ -257,6 +260,11 @@ COMPOSEEOF
         condition: service_healthy
     volumes:
       - ./frigate-notify/config.yml:/app/config.yml:ro
+
+networks:
+  caddy_net:
+    external: true
+    name: \${CADDY_NET:-caddy_net}
 COMPOSEEOF
     log_success "docker-compose.yml written"