refactor(event): replace global 60s inactivity timer with per-second tick event

Adds KEY_EVENT_SECOND_TICK, generated once per real second from
Clock_IncMS() via a new second_tick_flag and pushed through the normal
event queue, so every foreground App's onEvent() receives it and
decides independently whether to act. Removes the old global
inactivity_timer (60s sleep from anywhere) entirely. HomeApp now
accumulates its own idle-second counter and sleeps after 10s idle
specifically while on the home screen; MenuApp's existing 10s
auto-close is converted from onRun() polling to the same tick+reset
pattern for consistency. Any non-tick key event resets each app's own
counter to 0.

App/app_home.c

@@ -13,6 +13,12 @@
 extern SystemState current_state;
 extern volatile u16 ms_tick;
 
+// 待机时钟界面闲置多久自动进入低功耗休眠的门限 (秒)
+#define HOME_IDLE_SLEEP_SEC 10
+
+// 本应用私有变量：累计未按任何键的秒数 (由 KEY_EVENT_SECOND_TICK 驱动，任意按键事件清零)
+static u8 home_idle_sec = 0;
+
 // 声明本应用的生命周期回调函数
 static void HomeApp_OnStart(void);
 static void HomeApp_onRun(void);
@@ -34,6 +40,7 @@ WristbandApp home_app = {
  */
 static void HomeApp_OnStart(void)
 {
+    home_idle_sec = 0; // 重新进入待机主页 (开机/从菜单退回/休眠唤醒) 都清零闲置计数
     current_state = STATE_NORMAL;   // 系统切入正常待机状态
     RF_SetMode(1);                  // 开启天线并置为接收模式，监听无线探测器
 
@@ -80,6 +87,21 @@ static void HomeApp_onClose(void)
  */
 static EventResult HomeApp_onEvent(SystemEvent *evt)
 {
+    // 0. 整秒滴答：累计闲置秒数，达到门限就进入低功耗休眠
+    if (evt->key_event == KEY_EVENT_SECOND_TICK) {
+        home_idle_sec++;
+        if (home_idle_sec >= HOME_IDLE_SLEEP_SEC) {
+            home_idle_sec = 0;
+            current_state = STATE_SLEEP;      // 系统置为休眠状态
+            Enter_Low_Power_Sleep();          // 阻塞函数，MCU 在此挂起，唤醒后自动继续往下执行
+            AppManager_SwitchToForeground(&home_app); // 强制重新走一遍 OnStart，刷新画面和背光
+        }
+        return EVENT_HANDLED;
+    }
+
+    // 收到任意其它按键事件，说明用户仍在活动，清零闲置计数
+    home_idle_sec = 0;
+
     // 1. 长按 ■ 确认键，打开设置主菜单 MenuApp
     if (evt->key_event == KEY_EVENT_CONFIRM_LONG) {
         AppManager_SwitchToForeground(&menu_app);