Improve cart and dark mode UX

- Clear cart when customer logs out
- Hide cart bag button for non-authenticated users (only show for logged-in customers)
- Fix dark mode text visibility in all form inputs (input/textarea/select elements)

Addresses user request: cart should clear on logout and only be accessible to logged-in customers.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/app/cart/page.tsx

@@ -20,7 +20,7 @@ export default function CartPage() {
     window.location.href = '/checkout';
   };
 
-  if (!mounted) return null; // avoid a hydration mismatch on first paint
+  if (!mounted) return null;
 
   if (items.length === 0) {
     return (
@@ -163,9 +163,6 @@ export default function CartPage() {
         </div>
 
         <div className="w-full max-w-xs">
-          <div className="mb-4 rounded border border-splash-blue/40 bg-splash-blue/5 px-3 py-2 text-xs text-muted">
-            Your cart will be saved. You can log in or continue as a guest to complete your order.
-          </div>
           <button
             onClick={handleCheckout}
             className="w-full bg-clay px-6 py-3 text-sm font-medium text-paper transition-colors hover:bg-clay-dark"

src/app/globals.css

@@ -24,6 +24,11 @@
   body {
     @apply bg-paper text-ink font-body antialiased transition-colors duration-200;
   }
+  input,
+  textarea,
+  select {
+    @apply text-ink;
+  }
   ::selection {
     @apply bg-splash-pink text-paper;
   }