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/about.vue

@@ -104,7 +104,13 @@
   </PageShell>
 </template>
 
-<script setup></script>
+<script setup>
+useSiteMeta({
+  title: 'About',
+  description:
+    'A membership community for game developers exploring cooperative models. Three circles, pay what you can. A program of Baby Ghosts, a Canadian non-profit advancing cooperative practice in the game industry since 2023.',
+})
+</script>
 
 <style scoped>
 /* ---- ABOUT HERO ---- */