Update Transfer billing page copy for storage pricing.

Replace leftover QR Plus per-code billing text with Transfer retention pricing.

Co-authored-by: Cursor <cursoragent@cursor.com>

resources/views/qr/account/billing.blade.php

@@ -3,7 +3,7 @@
     @php $fmt = fn ($m) => 'GHS '.number_format($m / 100, 2); @endphp
     <div class="mx-auto max-w-3xl">
         <h1 class="text-xl font-semibold tracking-tight text-slate-900">Billing</h1>
-        <p class="mt-0.5 text-sm text-slate-500">QR code creation is billed from your Ladill wallet (GHS {{ number_format(config('qr.price_per_qr_ghs', 5), 2) }} per code).</p>
+        <p class="mt-0.5 text-sm text-slate-500">File storage is billed from your Ladill wallet (GHS {{ number_format(config('transfer.price_per_gb_month', 1), 2) }} per GB per month of retention).</p>
         <div class="mt-6 rounded-2xl border border-slate-200 bg-white p-6">
             <p class="text-xs font-medium uppercase tracking-wide text-slate-400">Current balance</p>
             <p class="mt-1 text-3xl font-semibold text-slate-900">{{ $fmt($balanceMinor) }}</p>