seo: refine social card — SVG mark, more spacing, cache-busting filename

- Use the transparent SVG brand mark instead of the dark-background PNG.
- Increase spacing between the headline and the feature chips.
- Rename the card to assets/social-card.png so browser/CDN/social caches
  fetch the new image instead of the stale og-image.png; repoint og:image,
  twitter:image and JSON-LD accordingly.

meta.json

@@ -1,10 +1,10 @@
 {
-  "version": "1782331597042",
-  "buildVersion": "1782331597042",
+  "version": "1782332019425",
+  "buildVersion": "1782332019425",
   "appVersion": "4.9.1",
-  "buildTime": "2026-06-24T20:06:37.081Z",
-  "buildId": "1782331597042-ae6900d",
-  "gitHash": "ae6900d",
+  "buildTime": "2026-06-24T20:13:39.462Z",
+  "buildId": "1782332019425-62567fb",
+  "gitHash": "62567fb",
   "generated": true,
-  "generatedAt": "2026-06-24T20:06:37.090Z"
+  "generatedAt": "2026-06-24T20:13:39.471Z"
 }