Initial scaffold: Researcher Endorsement frontend

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

src/components/Feed.tsx

@@ -0,0 +1,18 @@
+import React from 'react'
+import useAppStore from '../store/useAppStore'
+import PostCard from './PostCard'
+
+const Feed: React.FC = () => {
+  const posts = useAppStore((s) => s.posts)
+  const sorted = [...posts].sort((a,b) => b.createdAt - a.createdAt)
+  if (sorted.length === 0) return <div className="card">No posts yet.</div>
+  return (
+    <div>
+      {sorted.map((p) => (
+        <PostCard key={p.id} post={p} />
+      ))}
+    </div>
+  )
+}
+
+export default Feed