feat: серии + count-up в Stats

- SeriesGrid: карточки серий с иконками (Sparkles/Plug/Zap/Layers) и цветовыми темами
- /series/[slug]: страница серии с интро и сеткой статей в порядке из article_ids
- Stats: count-up анимация (easeOutQuart 1.2s) при появлении в viewport через IntersectionObserver
- sitemap.xml: добавлены /notes и все серии

app/sitemap.js

@@ -1,16 +1,18 @@
-import { listArticles, listTags } from '@/lib/engine';
+import { listArticles, listTags, listSeries } from '@/lib/engine';
 
 const SITE = 'https://zeropost.ru';
 
 export default async function sitemap() {
-  const [articles, tags] = await Promise.all([
+  const [articles, tags, series] = await Promise.all([
     listArticles({ limit: 200 }).catch(() => []),
     listTags().catch(() => []),
+    listSeries().catch(() => []),
   ]);
 
   const staticPages = [
     { url: `${SITE}/`, lastModified: new Date(), changeFrequency: 'daily', priority: 1 },
     { url: `${SITE}/about`, lastModified: new Date(), changeFrequency: 'monthly', priority: 0.5 },
+    { url: `${SITE}/notes`, lastModified: new Date(), changeFrequency: 'daily', priority: 0.6 },
   ];
 
   const articlePages = articles.map(a => ({
@@ -27,5 +29,12 @@ export default async function sitemap() {
     priority: 0.6,
   }));
 
-  return [...staticPages, ...articlePages, ...tagPages];
+  const seriesPages = series.map(s => ({
+    url: `${SITE}/series/${s.slug}`,
+    lastModified: s.updated_at ? new Date(s.updated_at) : new Date(),
+    changeFrequency: 'weekly',
+    priority: 0.7,
+  }));
+
+  return [...staticPages, ...articlePages, ...seriesPages, ...tagPages];
 }