qr: left-align the bookshop hero title on desktop

The title block used mx-auto max-w-md, so on a wide screen it floated in the
middle of a full-width cover image while everything else read left-to-right.
Released to the left edge from sm up.

Mobile is untouched: max-w-md already fills a phone screen, so mx-auto has no
visible effect there and the layout is unchanged.

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

resources/views/public/qr/landing.blade.php

@@ -1217,7 +1217,10 @@
             <div class="absolute inset-0" style="background: linear-gradient(145deg, {{ $aColor }}, {{ $aColor }}99);"></div>
         @endif
         <div class="absolute inset-x-0 bottom-0 px-5 pb-12 sm:pb-14">
-            <div class="mx-auto max-w-md text-white">
+            {{-- Mobile keeps the centred max-w-md column (which fills the screen
+                 anyway). From sm up the cover is far wider than that column, so the
+                 title is released to the left edge instead of floating mid-banner. --}}
+            <div class="mx-auto max-w-md text-white sm:mx-0">
                 <h1 class="text-2xl font-bold">{{ $aName }}</h1>
                 @if($aTagline)
                     <p class="mt-1 truncate text-sm text-white/90">{{ $aTagline }}</p>