fix: install updater alongside startup script

Download the update helper during install and expose it from the cloud server so new hosts can run manual updates immediately.

install_station_broadcast.lua

@@ -1,4 +1,5 @@
 local STATION_BROADCAST_URL = "http://stabadmin.fse-media.group/downloads/station_broadcast.lua"
+local UPDATE_SCRIPT_URL = "http://stabadmin.fse-media.group/downloads/update_station_broadcast.lua"
 
 local function fetch(url)
     if not http then
@@ -64,7 +65,8 @@ local function downloadTo(url, path)
 end
 
 local targets = {
-    { url = STATION_BROADCAST_URL, path = shell.resolve("/startup") }
+    { url = STATION_BROADCAST_URL, path = shell.resolve("/startup") },
+    { url = UPDATE_SCRIPT_URL, path = shell.resolve("/update_station_broadcast.lua") }
 }
 
 for _, t in ipairs(targets) do
@@ -76,4 +78,5 @@ for _, t in ipairs(targets) do
 end
 
 print("Install complete.")
+print("Update helper installed as /update_station_broadcast.lua")
 print("Run 'reboot' to start StationBroadcast on boot.")