fix: show one product per category on home (4 total)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/views/HomeView.vue

@@ -15,8 +15,17 @@ const categories = computed(() => {
   return Array.from(cats).sort()
 })
 
+const onePerCategory = computed(() => {
+  const seen = new Set<string>()
+  return products.value.filter((p) => {
+    if (seen.has(p.category)) return false
+    seen.add(p.category)
+    return true
+  })
+})
+
 const filtered = computed(() => {
-  if (!activeCategory.value) return products.value
+  if (!activeCategory.value) return onePerCategory.value
   return products.value.filter((p) => p.category === activeCategory.value)
 })