Offline addons, LAN-aware emergency hotspot, LAN time server

Offline bundle now carries every addon that works on a network without
internet: LMS (Lyrion's own .deb, from the addon's LMS_DEB_URL) +
Squeezelite, Asterisk Intercom (baresip), VNC, WireGuard and the
Emergency Hotspot packages - each list in a variable next to the code
that installs it (SQUEEZELITE_APT_PACKAGES, ASTERISK_INTERCOM_APT_PACKAGES,
VNC_APT_PACKAGES, WIREGUARD_APT_PACKAGES, EMERGENCY_HOTSPOT_APT_PACKAGES),
read by build-bundle.sh. Each install goes through
run_with_offline_fallback like CUPS, so they install offline from the
normal menus / Web UI. LMS installs as a bundle package when offline
(lms_offline_install_wanted); its online repo/direct-download paths are
unchanged. Tailscale/Netbird deliberately not bundled (vendor scripts,
vendor servers). Bundle: 524 MB (+87 MB).

Emergency hotspot: the boot check pinged only 8.8.8.8, so on a LAN with
no internet the hotspot started on every boot. Now chosen at setup:
"network" (default - router or internet must answer; a router that
ignores ping still counts if it answered ARP), "internet" (old check),
or "host" (a specific address). Three tries 10s apart. Existing scripts
keep the old check until Reconfigure.

New Core Settings -> Time Server (NTP) (menus/time_sync.sh): point
systemd-timesyncd at LAN time server(s) via a timesyncd.conf.d drop-in,
back to Ubuntu's defaults, or set the clock by hand (and the RTC) for a
network with no time server. Complete Uninstall resets it.

Also: lms_service_name used `systemctl list-unit-files | grep -q`, the
same pipefail/SIGPIPE pattern as the earlier cups_is_installed bug; now
`systemctl cat`.

Tested in a network-less chroot of the 26.04.1 server filesystem: kiosk
base, then action_wireguard_install and action_install_lms (real
functions) and the Squeezelite/Intercom/VNC/hotspot package sets all
installed from the bundle, apt left on normal sources after each.
Hotspot script generated for all three modes (plus an invalid address,
which falls back to "network") and its check run against simulated
networks: LAN-only with router answering ping or only ARP -> no hotspot
in "network" mode; nothing reachable -> hotspot. Time Server actions
driven with timedatectl stubbed: drop-in contents, input validation,
manual set-time sequence, reset removes the drop-in.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Cjz8a58eB5P9sUweqd3NHm

menus/complete_uninstall.sh

@@ -8,7 +8,7 @@
 # tailscale_do_uninstall, netbird_do_uninstall, lms_do_uninstall,
 # squeezelite_do_uninstall, asterisk_intercom_do_uninstall,
 # webui_do_uninstall, power_schedule_do_remove_all,
-# emergency_hotspot_do_disable) instead of
+# emergency_hotspot_do_disable, time_sync_do_reset) instead of
 # re-implementing removal logic for each addon a second time here - if an
 # addon's uninstall logic changes, this picks it up automatically. Only
 # the pieces no single addon owns - the kiosk user/files, Node.js/
@@ -62,6 +62,7 @@ action_complete_uninstall() {
     echo "  • LightDM and Openbox"
     echo "  • All kiosk schedules and services"
     echo "  • Emergency hotspot configuration"
+    echo "  • LAN time server setting (back to Ubuntu's defaults)"
     echo
     echo "⚠️  This CANNOT be undone!"
     echo
@@ -90,9 +91,10 @@ action_complete_uninstall() {
     asterisk_intercom_do_uninstall purge
     webui_do_uninstall
 
-    echo "[3/12] Removing schedules and emergency hotspot..."
+    echo "[3/12] Removing schedules, emergency hotspot and time server setting..."
     power_schedule_do_remove_all
     emergency_hotspot_do_disable
+    time_sync_do_reset
 
     # Must come after every addon teardown above - Asterisk Intercom's
     # helper still needs this user to resolve its systemd --user session.