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frontend/spa/src/components/ProductNotFound.vue

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+<template>
+  <div class="flex flex-col items-center justify-center text-center py-16">
+    <span class="text-5xl mb-4">😔</span>
+    <h2 class="text-xl font-semibold mb-2">Товар не найден</h2>
+    <p class="text-sm mb-4">К сожалению, запрошенный товар недоступен или был удалён.</p>
+    <button class="btn btn-primary" @click="goBack">
+      <svg xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="1.5" stroke="currentColor" class="size-6">
+        <path stroke-linecap="round" stroke-linejoin="round" d="M15.75 19.5 8.25 12l7.5-7.5" />
+      </svg>
+      Назад
+    </button>
+  </div>
+</template>
+
+<script setup>
+import { useRouter } from 'vue-router';
+const router = useRouter();
+const goBack = () => router.back();
+</script>