fix(front): clean localStorage on user change

- fix issue with selected drive and user logout/login via another user
    (was raising a "404 not found")
    - normalize all localStorage to "oxi-" prefix
    - add a specific frontend/AGENTS.md for frontend part (stop increasing the global AGENTS.md)

frontend/src/routes/s/[token]/+page.svelte

@@ -18,7 +18,7 @@
 	type Crumb = { id?: string; name: string };
 	type ViewMode = 'grid' | 'list';
 
-	const VIEW_KEY = 'oxicloud_share_view';
+	const VIEW_KEY = 'oxi-share-view';
 	const token = $derived(page.params.token ?? '');
 
 	let view = $state<State>('loading');