feat(seo): implement dynamic metadata, sitemap, and robots.txt

Add dynamic meta tags for routes and entity detail pages
Generate sitemap.xml and robots.txt dynamically in Vite
Change default frontend port from 3000 to 20015

frontend/src/views/ItemDetail.vue

@@ -12,6 +12,7 @@ import PokeBallMark from '../components/PokeBallMark.vue';
 import Skeleton from '../components/Skeleton.vue';
 import Tabs, { type TabOption } from '../components/Tabs.vue';
 import { iconAdd, iconBack, iconEdit, iconHabitat, iconItem } from '../icons';
+import { applySeo } from '../seo';
 import { api, getAuthToken, type AuthUser, type ItemDetail } from '../services/api';
 import ItemEdit from './ItemEdit.vue';
 
@@ -49,7 +50,17 @@ const customization = computed(() => {
 });
 
 async function loadItemDetail() {
-  item.value = await api.itemDetail(String(route.params.id));
+  const nextItem = await api.itemDetail(String(route.params.id));
+  item.value = nextItem;
+
+  if (route.meta.editorModal !== true) {
+    applySeo({
+      title: `${nextItem.name} - ${t('pages.items.title')}`,
+      description: t('seo.itemDetailDescription', { name: nextItem.name }),
+      canonicalPath: `/items/${nextItem.id}`,
+      image: nextItem.image?.url
+    });
+  }
 }
 
 onMounted(async () => {