fix: crop payment QR to square, removing green WeChat branding

Use object-fit:cover + object-position to crop the payment QR image
to a 1:1 aspect ratio, hiding the green header/footer branding that
clashed with the dark theme. Add consistent border to both QR images.

Author: AI Assistant

pricing.html

@@ -124,7 +124,8 @@
   font-size:.8rem;font-weight:700;display:flex;align-items:center;justify-content:center;margin:0 auto 10px;
   box-shadow:0 2px 8px rgba(199,70,52,.3)}
 .cta-qr-card-title{font-size:.95rem;font-weight:700;color:var(--text);margin-bottom:14px}
-.cta-qr-card .qr-img{max-width:180px;border-radius:var(--r)}
+.cta-qr-card .qr-img{max-width:180px;border-radius:var(--r);border:2px solid var(--border)}
+.cta-qr-pay .qr-img{max-width:200px;aspect-ratio:1/1;object-fit:cover;object-position:center 42%}
 .cta-qr-card .qr-note{font-size:.75rem;color:var(--accent2);margin-top:10px}
 .cta-qr-card .qr-label{font-size:.78rem;margin-top:10px}