Replace Create-rule header portraits with real PNGs so the circles paint.

The old SVG wrappers nested corrupt PNGs, so browsers fetched the files but showed empty rings.

Co-authored-by: Cursor <cursoragent@cursor.com>

.gitignore

@@ -50,6 +50,9 @@ npm-cache/
 # Marketing book cover (raster; see docs/guides/static-assets.md)
 !public/assets/marketing/community-rules-cover.png
 
+# Header Create-rule portraits
+!public/assets/marketing/avatar-*.png
+
 # Open Graph 1200×630 share images (`npm run generate:og-images`)
 !public/assets/marketing/og-image.png
 !public/assets/marketing/og-image-templates.png