Changed members list page to use ListPage

ref https://linear.app/tryghost/issue/DES-1378/

This completes the current admin list page migration sweep by moving members onto the shared Shade ListPage and PageHeader structure while keeping the members-specific table, filters, and sticky heading behavior local to the screen.

Author: peterzimon

apps/posts/src/views/members/components/members-content.tsx

@@ -197,7 +197,7 @@ function MembersList({
     };
 
     return (
-        <div ref={parentRef} className="-mt-4 w-full min-w-0 lg:-mt-8" data-testid="members-list-scroll-root">
+        <div ref={parentRef} className="w-full min-w-0" data-testid="members-list-scroll-root">
             <div
                 className="sticky z-[50] hidden overflow-visible bg-transparent lg:block"
                 style={{top: stickyTop}}