feat(content+admin): content ranking + statistics dashboard

- content-svc: template list gains popularity/rating sort modes (use_count_desc,
  popular, rating_desc); new PATCH /v1/templates/{id}/sort to set manual sort
  weight (feature/pin) without a full edit
- admin /admin/ranking: templates ordered by popularity with views/uses/rating
  and inline manual-sort editor
- admin /admin/stats: overview dashboard (users, revenue, paying customers,
  conversion, templates/categories/campaigns/blogs counts) aggregated from
  existing identity + content endpoints
- nav: Dashboard + Ranking links

Completes the epic: SMS/Email/Templates → Marketing → CRM → Ranking + Stats.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/[locale]/admin/layout.tsx

@@ -16,8 +16,10 @@ export default async function AdminLayout({
   }
   const t = await getTranslations("auto.appAdminLayout");
   const links: { href: string; label: string }[] = [
+    { href: "/admin/stats", label: t("stats") },
     { href: "/admin/categories", label: t("categories") },
     { href: "/admin/templates", label: t("templates") },
+    { href: "/admin/ranking", label: t("ranking") },
     { href: "/admin/tags", label: t("tags") },
     { href: "/admin/fonts", label: t("fonts") },
     { href: "/admin/blogs", label: t("blogs") },