Migrate LMS/Squeezelite addon; fix is_service_enabled dead pre-check; bump to v2.9.0

New menus/addon_lms_squeezelite.sh: install/reconfigure/uninstall for an
LMS (Lyrion/Logitech Media Server) server and a Squeezelite player,
wired into install.sh's Addons menu. Squeezelite's own start script and
systemd unit now go through $BIN_DIR/$SYSTEMD_DIR like every other
addon instead of hardcoded /usr/local/bin and /etc/systemd/system; LMS's
own apt repo/GPG key/ufw rules stay at their real fixed system paths,
same approach as CUPS.

Fixed a real unguarded-pipeline bug from the legacy install_lms():
`sudo systemctl enable "$service_name" 2>&1 | tee ...` made the exit
status depend on tee (always 0) instead of systemctl enable, silently
swallowing real enable/start failures. Now uses enable_and_start_units().

Fixed is_service_enabled() (shared helper, backported into the legacy
script too): its list-unit-files pre-check never matched a bare service
name, so it always fell through to "not enabled" regardless of the real
state. Dropped the dead pre-check.

Full command-level stubbed test suite covering install/reconfigure/
uninstall for both LMS and Squeezelite, including the repo-vs-fallback-
download path, undetectable-service-name path, and enable/start-failure
path. Full 12-suite regression + real end-to-end menu navigation via
install.sh all pass.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VfsFSoRqfbRG7XAg5RoE7e

install.sh

@@ -18,7 +18,8 @@
 #     Power/Display/Quiet Hours.
 #   Addons: CUPS Printing (menus/addon_cups.sh), Authelia Auto-Login
 #     (menus/addon_authelia.sh), Remote Access - VNC/WireGuard/
-#     Tailscale/Netbird (menus/addon_remote_access.sh).
+#     Tailscale/Netbird (menus/addon_remote_access.sh), LMS Server /
+#     Squeezelite Player (menus/addon_lms_squeezelite.sh).
 #   Advanced: Diagnostics (menus/diagnostics.sh - system status/logs/
 #     audio/network).
 #
@@ -58,6 +59,8 @@ source "$SCRIPT_DIR/menus/addon_cups.sh"
 source "$SCRIPT_DIR/menus/addon_authelia.sh"
 # shellcheck source=menus/addon_remote_access.sh
 source "$SCRIPT_DIR/menus/addon_remote_access.sh"
+# shellcheck source=menus/addon_lms_squeezelite.sh
+source "$SCRIPT_DIR/menus/addon_lms_squeezelite.sh"
 
 ################################################################################
 # Preflight
@@ -121,8 +124,8 @@ core_settings_menu() {
 }
 
 addons_menu_builder() {
-    MENU_LABELS=("CUPS Printing" "Authelia Auto-Login" "Remote Access")
-    MENU_HANDLERS=(addon_cups_menu addon_authelia_menu remote_access_menu)
+    MENU_LABELS=("CUPS Printing" "Authelia Auto-Login" "Remote Access" "LMS Server / Squeezelite Player")
+    MENU_HANDLERS=(addon_cups_menu addon_authelia_menu remote_access_menu addon_lms_squeezelite_menu)
 }
 
 addons_menu() {