Add admin Articles (CRUD) + Bans resources

- Articles: list / new / edit / delete (websiteArticles), unique-slug
  generation via slugify() (pure, unit-tested); staff-gated server actions.
- Bans: list active bans (ban_expire > now), create ban (writes the bans row +
  RCON disconnect) with type/duration/reason, lift ban; staff-gated actions.
- Admin nav extended (Articles, Bans).

Verified: tsc exit 0, vitest 48/48, next build exit 0 (7 /admin routes).

src/app/admin/articles/new/page.tsx

@@ -0,0 +1,20 @@
+import Link from "next/link";
+import { createArticle } from "@/actions/admin-articles";
+
+export default function NewArticle() {
+  return (
+    <main>
+      <p className="muted">
+        <Link href="/admin/articles">← Articles</Link>
+      </p>
+      <h1>New article</h1>
+      <form action={createArticle} className="card" style={{ display: "grid", gap: "0.6rem" }}>
+        <input name="title" placeholder="Title" required />
+        <input name="image" placeholder="Image URL" />
+        <textarea name="shortStory" placeholder="Short story (summary)" rows={2} />
+        <textarea name="fullStory" placeholder="Full story" rows={10} />
+        <button type="submit">Create</button>
+      </form>
+    </main>
+  );
+}