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

lib/common.sh

@@ -320,7 +320,7 @@ configure_caddy_for_service() {
 
 # $SERVICE_NAME
 $SERVICE_DOMAIN {
-    reverse_proxy localhost:$SERVICE_PORT
+    reverse_proxy host.docker.internal:$SERVICE_PORT
 
     # Security headers
     header {