fix(admin): persist data directory and pass env vars

app/admin/medien/page.tsx

@@ -0,0 +1,47 @@
+import { mkdir, readdir } from "fs/promises";
+import path from "path";
+import Image from "next/image";
+import { redirect } from "next/navigation";
+import AdminShell from "@/components/admin/AdminShell";
+import { requireAdminSession } from "@/lib/admin/auth";
+
+const uploadDir = path.join(process.cwd(), "public", "uploads", "images");
+
+async function getFiles() {
+  await mkdir(uploadDir, { recursive: true });
+  return readdir(uploadDir);
+}
+
+export default async function AdminMediaPage() {
+  if (!await requireAdminSession()) redirect("/admin/login");
+  const files = await getFiles();
+
+  return (
+    <AdminShell>
+      <div className="admin-page-head">
+        <p className="eyebrow">Assets</p>
+        <h1>Medienverwaltung</h1>
+      </div>
+      <form className="admin-card admin-upload" action="/api/admin/media" method="post" encType="multipart/form-data">
+        <label>Datei hochladen<input name="file" type="file" accept="image/jpeg,image/png,image/webp,application/pdf" /></label>
+        <button className="button" type="submit">Datei hochladen</button>
+      </form>
+      <section className="admin-card">
+        <h2>Uploads</h2>
+        <div className="media-grid">
+          {files.map((file) => {
+            const url = `/uploads/images/${file}`;
+            return (
+              <a key={file} className="media-item" href={url} target="_blank" rel="noreferrer">
+                {/\.(png|jpe?g|webp)$/i.test(file)
+                  ? <Image src={url} alt={file} width={320} height={220} />
+                  : <span>{file}</span>}
+              </a>
+            );
+          })}
+          {files.length === 0 && <p className="admin-muted">Noch keine Uploads vorhanden.</p>}
+        </div>
+      </section>
+    </AdminShell>
+  );
+}