refactor(frontend): EmptyState + LoadingSkeleton primitives; unified ThoughtForm replaces PostThoughtForm and ReplyForm

thoughts-frontend/app/page.tsx

@@ -7,7 +7,8 @@ import {
   getTopFriends,
   Me,
 } from "@/lib/api";
-import { PostThoughtForm } from "@/components/post-thought-form";
+import { ThoughtForm } from "@/components/thought-form";
+import { EmptyState } from "@/components/empty-state";
 import { Button } from "@/components/ui/button";
 import Link from "next/link";
 import { PopularTags } from "@/components/popular-tags";
@@ -80,7 +81,7 @@ async function FeedPage({
           <header className="mb-6">
             <h1 className="text-3xl font-bold text-shadow-sm">Your Feed</h1>
           </header>
-          <PostThoughtForm />
+          <ThoughtForm />
 
           <div className="block lg:hidden space-y-6">
             <PopularTags />
@@ -102,9 +103,7 @@ async function FeedPage({
               />
             ))}
             {thoughtThreads.length === 0 && (
-              <p className="text-center text-muted-foreground pt-8">
-                Your feed is empty. Follow some users to see their thoughts!
-              </p>
+              <EmptyState message="Your feed is empty. Follow some users to see their thoughts!" />
             )}
           </div>
           <PaginationNav