add base padding to themed-input and fix contact form selector

themed-input had no padding in the base style, so inputs were rendering
with browser-default 1px/2px padding. Added 0.5rem 0.75rem as the base.

Also fixed the contact form CSS which was targeting .shop-input (a class
that doesn't exist on rendered elements) instead of .themed-input.

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

assets/css/theme-layer2-attributes.css

@@ -249,6 +249,7 @@
     color: var(--t-text-primary);
     border: 1px solid var(--t-border-default);
     border-radius: var(--t-radius-input);
+    padding: 0.5rem 0.75rem;
 
     &:focus {
       outline: none;