fix(client): 修复多个同名同目的地的列车互相清除 pending 状态的问题

当存在多个列车（如无名列车 ??? 开往同一目的地）时：
- 第二个 ETA 较远的列车会因为 `etaSeconds > 45` 走进 `else` 分支
- 原逻辑在 `else` 分支会直接清空该 key 的 pending 状态
- 导致排在前面的列车永远无法积累 5 秒的稳定期

修改：
1. 移除 `else` 分支，统一交由末尾的清理循环处理
2. 使用 `if not seenApproachKeys[announceKey]` 确保同一个 tick 只有 ETA 最近（排最前）的列车更新状态

station_broadcast.lua

@@ -1,6 +1,6 @@
 
 -- 1. Configuration & Constants
-local APP_VERSION_TEXT = "v1.0.50"
+local APP_VERSION_TEXT = "v1.0.51"
 
 local CONFIG = {
     CLOUD_URL = "ws://stabadmin.fse-media.group",
@@ -2704,6 +2704,7 @@ function Main.loop()
                         end
                         
                         if etaSeconds >= 0 and etaSeconds <= 45 then
+                            if not seenApproachKeys[announceKey] then
                                 seenApproachKeys[announceKey] = true
                                 local pending = State.pendingApproaching[announceKey]
                                 if not pending then
@@ -2734,8 +2735,7 @@ function Main.loop()
                                         reason = reason
                                     })
                                 end
-                        else
-                            State.pendingApproaching[announceKey] = nil
+                            end
                         end
                     end
                 end
@@ -2838,12 +2838,13 @@ function Main.loop()
                         end
 
                         if etaSeconds >= 0 and etaSeconds <= 45 then
+                            if not seenApproachKeys[announceKey] then
                                 seenApproachKeys[announceKey] = true
                                 local pending = State.pendingApproaching[announceKey]
                                 if not pending then
                                     State.pendingApproaching[announceKey] = { since = now, lastEta = etaSeconds }
                                 else
-                                if etaSeconds > (tonumber(pending.lastEta) or etaSeconds) + 3 then
+                                    if etaSeconds > (tonumber(pending.lastEta) or etaSeconds) + 15 then
                                         pending.since = now
                                     end
                                     pending.lastEta = etaSeconds
@@ -2866,8 +2867,7 @@ function Main.loop()
                                         delay = delay
                                     })
                                 end
-                        else
-                            State.pendingApproaching[announceKey] = nil
+                            end
                         end
                     end
                 end