feat: 明确音频优先级，优化发车音频触发时机

- 到达与发车最高优先级(3)，其次是进站预告(2)，然后是延误警告(1)，最低为背景音乐(0)

- 将发车音乐的触发时机从固定时间改为动态计算（音频时长+1.5秒补偿），确保音频结束时列车刚好发车

- 拆分 handleTrainApproaching 与 handleTrainAlert 逻辑，解耦进站与延误的优先级

- 版本号提升至 v1.0.59

station_broadcast.lua

@@ -1,6 +1,6 @@
 
 -- 1. Configuration & Constants
-local APP_VERSION_TEXT = "v1.0.58"
+local APP_VERSION_TEXT = "v1.0.59"
 
 local CONFIG = {
     CLOUD_URL = "ws://stabadmin.fse-media.group",
@@ -2161,6 +2161,11 @@ function Network.messageLoop()
                         local flushBelow = data.flushBelow
                         Audio.stop(mode, flushBelow)
                     end
+                elseif data.type == "train_arrival_ack" then
+                    if State.currentTrain and State.currentTrain.id == data.trainId then
+                        State.currentTrain.departureDuration = tonumber(data.departureDuration) or 10
+                        Utils.log("INFO", "Got departure audio duration: " .. State.currentTrain.departureDuration .. "s")
+                    end
                 elseif data.type == "station_update" then
                     local targetVersion = AutoUpdate.getTargetVersion(data)
                     if targetVersion == "" then
@@ -2752,7 +2757,7 @@ function Main.loop()
                                 State.announcedAlerts[alertKey] = now
                                 Utils.log("INFO", string.format("Train Alert: %s (ETA: %ds, Delay: %dm, Cancelled: %s, Reason: %s)", trainName, etaSeconds, displayDelayMinutes, tostring(cancelled), tostring(reason or "")))
                                 Network.send({
-                                    type = "train_approaching",
+                                    type = "train_alert",
                                     stationName = State.stationName,
                                     stationCode = State.stationCode,
                                     stationPlatform = platform,
@@ -2908,7 +2913,7 @@ function Main.loop()
                                 State.announcedAlerts[alertKey] = now
                                 Utils.log("INFO", string.format("Train Delay Alert: %s (ETA: %ds, Delay: %dm)", tName, etaSeconds, delay))
                                 Network.send({
-                                    type = "train_approaching",
+                                    type = "train_alert",
                                     stationName = State.stationName,
                                     stationCode = State.stationCode,
                                     stationPlatform = platform or State.stationPlatform or "1",
@@ -3029,11 +3034,14 @@ function Main.loop()
                     trainId = id,
                     destination = dest,
                     nextStation = nextStation,
-                    departureTime = State.currentTrain.departureTime
+                    departureTime = State.currentTrain.departureTime,
+                    departureBeep = State.departureBeep
                 })
             else
                 local now = os.epoch("utc") / 1000
-                if not State.currentTrain.departureSent and (State.currentTrain.departureTime - now) <= 10 then
+                -- 增加 1.5 秒网络与预缓冲补偿，确保音频结束时列车刚好发车
+                local triggerOffset = (State.currentTrain.departureDuration or 10) + 1.5
+                if not State.currentTrain.departureSent and (State.currentTrain.departureTime - now) <= triggerOffset then
                     State.currentTrain.departureSent = true
                     Network.send({
                         type = "train_departure",