feat(launcher): implement device heartbeat and background sync engine

- Hardened 'find_object_id' in Dexie to support 'event_' prefixed IDs.
- Implemented singleton 'LauncherBackgroundSync' in root launcher layout.
- Added V3-compliant heartbeat and room refresh cycles.
- Fixed redundant component imports and Skeleton UI prop errors.
- Added 'inc_file_li' support to event API loader.

src/lib/elements/element_codemirror_editor.svelte

@@ -10,7 +10,7 @@
 
     let { content = $bindable(''), placeholder = 'Start typing...' }: Props = $props();
 
-    let editor_container: HTMLDivElement = $state();
+    let editor_container: HTMLDivElement | undefined = $state();
     let editor_view: any;
     let cm: any; // Declare cm at the top level