fix(nav): prevent global header overflow at lg breakpoint (1024px)

- Upload button text wrapped in hidden xl:inline to hide label below xl
- AppNav logo margin reduced from mr-10 to mr-4 xl:mr-10 at lg breakpoint
  Combined these changes bring the header content to ~923px vs ~945px
  available space at 1024px, eliminating horizontal overflow

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/AppNav.svelte

@@ -29,7 +29,7 @@ function handleOverlayKeydown(event: KeyboardEvent) {
 </script>
 
 <div class="flex items-stretch">
-	<div class="mr-10 flex flex-shrink-0 items-center">
+	<div class="mr-4 flex flex-shrink-0 items-center xl:mr-10">
 		<a href="/" class="flex items-center" aria-label="Familienarchiv">
 			<span class="font-sans text-xl font-bold tracking-widest text-white uppercase"
 				>Familienarchiv</span