feat(drive): add drive picker in sidebar

- select by default the home drive

frontend/src/routes/+page.svelte

@@ -1,10 +1,18 @@
 <script lang="ts">
 	import { goto } from '$app/navigation';
 	import { onMount } from 'svelte';
+	import { session } from '$lib/stores/session.svelte';
 
-	// The app root redirects to the primary files view.
+	// The app root redirects by user kind:
+	//   - external users (magic-link / OIDC-only / OCM recipients) have no
+	//     personal drive, so they land on Shared-with-me;
+	//   - internal users go to the files browser, which resolves the default
+	//     personal drive's root folder via `session.loadHomeFolder()` (post-D0
+	//     this reads `GET /api/drives` and picks the row whose
+	//     `default_for_user` matches the caller).
 	onMount(() => {
-		void goto('/files', { replaceState: true });
+		const target = session.isExternalUser ? '/shared-with-me' : '/files';
+		void goto(target, { replaceState: true });
 	});
 </script>