Apply the local/remote Caddy mode resolution to every service, not just traccar

traccar.sh's caddy_net wiring was fixed to mirror configure_caddy_for_service's
own mode resolution (CADDY_MODE from site config, then a local ~/docker/caddy,
then the legacy CADDY_REMOTE_HOST var) instead of only checking for the local
directory. That same bare directory check was copy-pasted into the caddy_net
wiring of every other Docker service in the repo, so a site with Caddy on a
different box would silently fail to join any of their containers to caddy_net
during setup (or, for homeassistant/koha, only get half the wiring right).

Applied the same fix mechanically across all 37 services using the standard
_CADDY_NET_BLOCK/_CADDY_NET_SECTION pattern (verified identical text via
scripted diff before touching any of them), plus by hand for:
- homeassistant.sh and koha.sh, which use their own differently-shaped
  variables (HA_CADDY_NET_LINES / _CADDY_NET_ENTRY) for the same decision
- paintplus.sh and ai-stack.sh, which do a live `docker network connect`
  instead of a compose network block
- watchyourlan.sh, whose Caddy note was worded for local-only setups

sms-inbound.sh got more than a mode swap: its Caddy wiring was hand-rolled
(not routed through configure_caddy_for_service) and had no remote-Caddy
path at all — a remote Caddy box would get a misleading "Caddy isn't
installed here" message instead of a snippet. Added
_sms_write_caddy_snippet(), mirroring the snippet-file pattern
configure_caddy_for_service uses everywhere else, and pointed the firewall
gate at the same three-way mode instead of a two-way dir check.

Verified: bash -n across all of services/*.sh, a scripted check that every
touched file has exactly one _CADDY_MODE resolution and no leftover bare
`[ -d "$DOCKER_DIR/caddy" ]` feeding a caddy_net decision, and spot-checked
docker compose config renders (traccar, mattermost) confirming the ${VAR}
interpolation and multi-service usage sites still resolve correctly.

services/ai-stack.sh

@@ -218,7 +218,15 @@ GPUEOF
 
     # ── Caddy (Open WebUI has built-in auth — no Authelia) ────────────────────
     # The generated compose doesn't join caddy_net, so attach the container by name.
-    if [ -d "$DOCKER_DIR/caddy" ] && [ "$INSTALLER_RAN" = true ]; then
+    # Mirrors configure_caddy_for_service's own mode resolution (lib/common.sh):
+    # explicit CADDY_MODE from the site config wins, then a local ~/docker/caddy,
+    # then the legacy CADDY_REMOTE_HOST var. Only "local" joins caddy_net — a
+    # remote Caddy box can't reach this container by name over a bridge network
+    # it isn't on anyway.
+    local _CADDY_MODE="${CADDY_MODE:-none}"
+    [ "$_CADDY_MODE" = "none" ] && [ -d "$DOCKER_DIR/caddy" ] && _CADDY_MODE="local"
+    [ "$_CADDY_MODE" = "none" ] && [ -n "${CADDY_REMOTE_HOST:-}" ] && _CADDY_MODE="remote"
+    if [ "$_CADDY_MODE" = "local" ] && [ "$INSTALLER_RAN" = true ]; then
         docker network connect "$SITE_CADDY_NET" open-webui 2>/dev/null || true
     fi
     configure_caddy_for_service "Open WebUI" "open-webui:8080" "ai"