style: unify all empty states to shared .empty-state class across all modules

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

public/styles/shopping.css

@@ -416,36 +416,6 @@
 
 .item-delete:hover { color: var(--color-danger); }
 
-/* --------------------------------------------------------
- * Leer-Zustand
- * -------------------------------------------------------- */
-.shopping-empty {
-  display: flex;
-  flex-direction: column;
-  align-items: center;
-  justify-content: center;
-  padding: var(--space-12) var(--space-6);
-  text-align: center;
-  flex: 1;
-}
-
-.shopping-empty__icon {
-  width: 56px;
-  height: 56px;
-  color: var(--color-text-disabled);
-  margin-bottom: var(--space-4);
-}
-
-.shopping-empty__title {
-  font-size: var(--text-lg);
-  font-weight: var(--font-weight-semibold);
-  margin-bottom: var(--space-2);
-}
-
-.shopping-empty__desc {
-  font-size: var(--text-sm);
-  color: var(--color-text-secondary);
-}
 
 /* --------------------------------------------------------
  * No-Lists-Zustand