Add admin UI + MinIO image uploads

- Admin API: list/edit posts (incl. drafts, raw markdown), moderate comments, subscribers,
  author bio/links, and presigned image upload to MinIO (bucket is public-read for covers).
- Admin UI at /admin: post editor with cover-image upload, comment moderation, subscriber list.
- Public security switched to authenticated-paths so static assets (/images, /data) stay public.

frontend/src/pages/AuthorPage.tsx

@@ -1,48 +0,0 @@
-import { Link, useParams } from 'react-router-dom';
-import { getAuthor } from '../api';
-import { useAsync } from '../lib/useAsync';
-import PostCard from '../components/PostCard';
-
-export default function AuthorPage() {
-  const { name = '' } = useParams();
-  const { data: author, loading, error } = useAsync(() => getAuthor(name), [name]);
-
-  if (loading) return <p className="text-primary-500">Loading…</p>;
-  if (error || !author) {
-    return (
-      <div className="mx-auto max-w-3xl">
-        <h1 className="mb-4 text-3xl font-bold">Author not found</h1>
-        <p className="text-primary-700"><Link to="/authors">See all authors</Link>.</p>
-      </div>
-    );
-  }
-
-  return (
-    <div className="mx-auto max-w-5xl">
-      <div className="card mb-10">
-        <div className="flex items-center gap-6">
-          {author.pfpLink && (
-            <img src={author.pfpLink} alt={author.name} className="h-24 w-24 rounded-full object-cover" />
-          )}
-          <div>
-            <h1 className="mb-1 text-3xl font-bold">{author.name}</h1>
-            <p className="text-primary-500">
-              {author.postCount} {author.postCount === 1 ? 'post' : 'posts'}
-            </p>
-          </div>
-        </div>
-        {author.bio && <p className="mt-6 text-primary-700">{author.bio}</p>}
-        <div className="mt-4 flex gap-4">
-          {author.xLink && <a href={author.xLink} target="_blank" rel="noreferrer">X</a>}
-          {author.fbLink && <a href={author.fbLink} target="_blank" rel="noreferrer">Facebook</a>}
-          {author.instaLink && <a href={author.instaLink} target="_blank" rel="noreferrer">Instagram</a>}
-        </div>
-      </div>
-
-      <h2 className="mb-6 border-b border-primary-200 pb-2 text-2xl font-bold">Posts</h2>
-      <div className="grid grid-cols-1 gap-6 md:grid-cols-2">
-        {author.posts.map((post) => <PostCard key={post.slug} post={post} />)}
-      </div>
-    </div>
-  );
-}