fix: dashboard title buttons responsiveness on mobile devices

src/lib/components/layout/DashboardHeader.svelte

@@ -10,12 +10,12 @@
 	const t = $derived(languageStore.t);
 </script>
 
-<div class="flex items-center justify-between">
-	<div>
+<div class="flex flex-col gap-4 sm:flex-row sm:items-center sm:justify-between">
+	<div class="flex-1 min-w-0">
 		<h1 class="text-3xl font-bold">{t.nav.dashboard}</h1>
-		<p class="text-muted-foreground">{t.dashboard.welcomeBack}, {userName || userEmail}</p>
+		<p class="text-muted-foreground truncate">{t.dashboard.welcomeBack}, {userName || userEmail}</p>
 	</div>
-	<div class="flex items-center gap-1 sm:gap-2">
+	<div class="flex items-center gap-1 sm:gap-2 flex-shrink-0">
 		<LanguageToggle />
 		<ThemeToggle />
 		<Button variant="outline" onclick={() => signOut({ callbackUrl: '/' })}>{t.auth.signOut}</Button>