feat: add Indicator LED control capability with session keepalive refs #4875

Add a CanIndicatorLight capability and status-aware Indicator toggle button. The indicator LED on the ASH21-B, ADC2W and ASH42-B is controlled via the LightGlobal config (configManager get/setConfig); add indicatorLightOn/Off/Status to Dahua_RPC and a model-specific 'Amcrest ASH42-B RPC' Controls row, with the capability also enabled on the ASH21-B/ADC2W/generic rows. Migration zm_update-1.39.13.sql adds the column.

Add Dahua_RPC keepAlive (global.keepAlive) wired into a 30s zmcontrol idle tick, plus session-expiry re-login retry in set_config and the status queries, so the long-running control daemon does not silently fail after the ~60s session timeout.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/includes/Control.php

@@ -99,6 +99,7 @@ class Control extends ZM_Object {
     'MinWhiteSpeed' => NULL,
     'MaxWhiteSpeed' => NULL,
     'CanLight' => 0,
+    'CanIndicatorLight' => 0,
     'HasPresets' => 0,
     'NumPresets' => 0,
     'HasHomePreset' => 0,
@@ -125,6 +126,8 @@ class Control extends ZM_Object {
     $cmds['Reboot'] = 'reboot';
     $cmds['LightOn']  = 'lightOn';
     $cmds['LightOff'] = 'lightOff';
+    $cmds['IndicatorLightOn']  = 'indicatorLightOn';
+    $cmds['IndicatorLightOff'] = 'indicatorLightOff';
 
     $cmds['PresetSet'] = 'presetSet';
     $cmds['PresetGoto'] = 'presetGoto';