Keep monitor always on and switch Home layout to horizontal 90/10

- Removed ScreenManager idle sleep entirely (constructor no longer starts
  the idle monitor, setIdleTimeout is now a no-op, unused fields and the
  private startIdleMonitor method removed). Display never sleeps; the
  photo frame provides the idle visual instead.
- DashboardContent now uses flex-row: calendar 90% wide, todo 10% wide.

src/App.tsx

@@ -100,14 +100,14 @@ function DashboardContent() {
   const config = useSettingsStore((state) => state.config);
 
   return (
-    <div className="col-span-12 flex flex-col gap-3 min-h-0">
+    <div className="col-span-12 flex flex-row gap-3 min-h-0">
       {config.calendar && (
-        <div className="flex-[9] min-h-0">
+        <div className="flex-[9] min-w-0">
           <CalendarWidget />
         </div>
       )}
       {config.todoList && (
-        <div className="flex-[1] min-h-0">
+        <div className="flex-[1] min-w-0">
           <TodoWidget />
         </div>
       )}