Kiosk: apply schedule engine in playback and add System Settings toggle

ScrollerPage now resolves the active Block from ScheduleManager (reusing
the existing stream-switch path), honoring dynamicAudio true/false and
falling back to local selection for gaps, no schedule, or toggle off.
Adds a 'Schedule' On/Off entry (default On) in System Settings persisted
in config.yaml, and config plumbing (proclamation.schedule_enabled). All
on-device schedule times remain 12h AM/PM.

src/config/config_manager.cpp

@@ -253,6 +253,9 @@ void ConfigManager::loadAndMergeDefaults() {
         if (proc_node.hasChild("schedule_active")) {
             merged.proclamation.schedule_active = proc_node.getChild("schedule_active").asBool(defaults.proclamation.schedule_active);
         }
+        if (proc_node.hasChild("schedule_enabled")) {
+            merged.proclamation.schedule_enabled = proc_node.getChild("schedule_enabled").asBool(defaults.proclamation.schedule_enabled);
+        }
     }
 
     {