Move the use-case index onto Learn so the pilot stories stay reachable, and make share images resolve on the host that serves the page.

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

public/content/blog/how-communityrule-works-horizontal.svg

@@ -0,0 +1,3 @@
+<svg width="320" height="226" viewBox="0 0 320 226" fill="none" xmlns="http://www.w3.org/2000/svg">
+  <rect width="320" height="226" fill="#FEFCC9"/>
+</svg>