feat(website): add OG hero preview image for link sharing

Replace the raw logo OG image with a designed 1200×630 hero card
generated at build time using satori + @resvg/resvg-js.

- Add generate-og.ts script with branded dark card design (gradient
  orbs, geometric rings, logo, title, tagline)
- Wire generation into build pipeline (runs before astro build)
- Update meta tags with absolute URLs, dimensions, and twitter:image
- Configure site URL (https://aryx.app) in astro.config.mjs

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

website/package.json

@@ -5,12 +5,17 @@
   "type": "module",
   "scripts": {
     "dev": "astro dev",
-    "build": "astro build",
+    "generate:og": "bun run scripts/generate-og.ts",
+    "build": "bun run generate:og && astro build",
     "preview": "astro preview"
   },
   "dependencies": {
     "astro": "^5.7.10",
     "@tailwindcss/vite": "^4.1.4",
     "tailwindcss": "^4.1.4"
+  },
+  "devDependencies": {
+    "@resvg/resvg-js": "^2.6.2",
+    "satori": "^0.26.0"
   }
 }