feat(core): bettery save mode (#12996)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Introduced a battery save mode that can pause background sync and
processing to conserve energy.
* Battery save mode is automatically enabled when the app window loses
focus and disabled when the window regains focus or is interacted with.
  * Available in both web and desktop (Electron) versions.

* **Improvements**
* Added user activity detection to optimize background operations for
better battery efficiency.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/apps/electron-renderer/src/app/effects/store-manager.ts

@@ -46,6 +46,15 @@ export function setupStoreManager(framework: Framework) {
   window.addEventListener('beforeunload', () => {
     storeManagerClient.dispose();
   });
+  window.addEventListener('focus', () => {
+    storeManagerClient.disableBatterySaveMode();
+  });
+  window.addEventListener('click', () => {
+    storeManagerClient.disableBatterySaveMode();
+  });
+  window.addEventListener('blur', () => {
+    storeManagerClient.enableBatterySaveMode();
+  });
 
   framework.impl(NbstoreProvider, {
     openStore(key, options) {