fix(services): conditional caddy_net across all Docker service scripts

Only include the caddy_net network block in generated docker-compose.yml
files when ~/docker/caddy exists. Prevents "network caddy_net declared
as external, but could not be found" on standalone installs without Caddy.

Affected: actualbudget, archivebox, arm, audiobookshelf, calibre-web,
changedetection, drum-rhythm-game, emby, fmd, frigate, frigate-audio,
frigate-notify, gatus, homeassistant, immich, iopaint, jellyfin, joplin,
koha, lyrion, magicmirror, mail-archiver, mattermost, mealie, meshcentral,
n8n, nextcloud, ntfy, onlyoffice, portainer, stirling-pdf, syncthing,
traccar, unifi, uptimekuma, vaultwarden, wg-easy

Skipped: authelia (creates caddy_net itself), caddy, crowdsec, wolf,
wolf-pair, and services using network_mode: host with no caddy_net.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01D8ckUJQtj1pH8jtAddBDZs

services/arm.sh

@@ -233,6 +233,23 @@ install_arm() {
     TZ_VAL="${SITE_TZ:-$(cat /etc/timezone 2>/dev/null || echo UTC)}"
     UID_VAL=$(id -u "$ACTUAL_USER"); GID_VAL=$(id -g "$ACTUAL_USER")
 
+    local _CADDY_NET_BLOCK=""
+    if [ -d "$DOCKER_DIR/caddy" ]; then
+        _CADDY_NET_BLOCK="    networks:
+      - caddy_net
+"
+    fi
+
+    local _CADDY_NET_SECTION=""
+    if [ -d "$DOCKER_DIR/caddy" ]; then
+        _CADDY_NET_SECTION="
+networks:
+  caddy_net:
+    external: true
+    name: ${SITE_CADDY_NET:-caddy_net}
+"
+    fi
+
     cat > docker-compose.yml << ARM_COMPOSE
 name: arm
 
@@ -258,13 +275,7 @@ services:
       # Add more optical drives as needed:
       # - /dev/sr1:/dev/sr1
     privileged: true
-    networks:
-      - caddy_net
-
-networks:
-  caddy_net:
-    external: true
-    name: \${CADDY_NET:-caddy_net}
+${_CADDY_NET_BLOCK}${_CADDY_NET_SECTION}
 ARM_COMPOSE
 
     cat > .env << ARM_ENV