feat(seo): site meta composable + Open Graph image generation

Adds `useSiteMeta()` composable that wraps useSeoMeta with site defaults
(title template, canonical URL, og/twitter image, og:site_name) and
absolute-URL handling via runtimeConfig.public.appUrl.

Adds /og/events/[slug].png route that renders per-event OG images via
satori + @resvg/resvg-js, cached on disk by slug + updatedAt. Bundles
Brygada 1918 + Commit Mono fonts as server assets, ships a fallback
default.png, and patches @shuding/opentype.js via patch-package.

Converts ~25 pages from useHead to useSiteMeta and adds noindex on
private/auth/admin pages.

app/pages/member/dashboard.vue

@@ -220,6 +220,8 @@
 </template>
 
 <script setup>
+useSiteMeta({ title: 'Dashboard', noindex: true });
+
 const { memberData, checkMemberStatus } = useAuth();
 const { isActive, statusConfig, isPendingPayment, canPeerSupport } =
   useMemberStatus();