fix(admin): make admin panel layout responsive on mobile

The permanent 224px sidebar in the admin layout had no responsive
handling at all, leaving almost no width for content on a phone
(Gitea #10). Sidebar is now hidden below md: and replaced by a
topbar + slide-in Sheet drawer (AdminMobileNav) with the same nav
links; content padding and the outer flex direction adapt per
breakpoint.

src/app/p/[secret]/layout.tsx

@@ -3,6 +3,7 @@ import { auth } from "@clerk/nextjs/server";
 import Link from "next/link";
 import { createTRPCCaller } from "@/trpc/server";
 import { timingSafeStringEqual } from "@/lib/timing-safe-compare";
+import { AdminMobileNav } from "@/components/admin/AdminMobileNav";
 import {
   LayoutDashboard,
   Users,
@@ -71,10 +72,19 @@ export default async function AdminLayout({ children, params }: AdminLayoutProps
       : []),
   ];
 
+  const navForMobile = nav.map(({ href, label, Icon }) => ({
+    href,
+    label,
+    icon: <Icon className="h-4 w-4 shrink-0" />,
+  }));
+
   return (
-    <div className="flex min-h-screen bg-zinc-950 text-zinc-100">
-      {/* Sidebar */}
-      <aside className="w-56 shrink-0 border-r border-zinc-800 flex flex-col py-6 px-4 gap-1 h-screen sticky top-0 overflow-y-auto">
+    <div className="flex min-h-screen flex-col bg-zinc-950 text-zinc-100 md:flex-row">
+      {/* Mobile topbar + drawer — hidden md: and up */}
+      <AdminMobileNav nav={navForMobile} />
+
+      {/* Sidebar — hidden below md:, permanent from md: up */}
+      <aside className="hidden md:flex w-56 shrink-0 border-r border-zinc-800 flex-col py-6 px-4 gap-1 h-screen sticky top-0 overflow-y-auto">
         <p className="text-xs font-semibold text-zinc-500 uppercase tracking-widest px-2 mb-3">
           PawFeed Admin
         </p>
@@ -101,7 +111,7 @@ export default async function AdminLayout({ children, params }: AdminLayoutProps
       </aside>
 
       {/* Content */}
-      <main className="flex-1 overflow-auto p-8">{children}</main>
+      <main className="min-w-0 flex-1 overflow-auto p-4 md:p-8">{children}</main>
     </div>
   );
 }

src/components/admin/AdminMobileNav.tsx

@@ -0,0 +1,77 @@
+"use client";
+
+import { useState } from "react";
+import Link from "next/link";
+import { Menu, ArrowLeft } from "lucide-react";
+import {
+  Sheet,
+  SheetClose,
+  SheetContent,
+  SheetHeader,
+  SheetTitle,
+  SheetTrigger,
+} from "@/components/ui/sheet";
+import { Button } from "@/components/ui/button";
+
+interface AdminMobileNavProps {
+  nav: { href: string; label: string; icon: React.ReactNode }[];
+}
+
+/**
+ * Mobile topbar + slide-in nav drawer for the admin panel — the desktop
+ * <aside> sidebar in layout.tsx is hidden below md: and replaced by this.
+ */
+export function AdminMobileNav({ nav }: AdminMobileNavProps) {
+  const [open, setOpen] = useState(false);
+
+  return (
+    <div className="md:hidden sticky top-0 z-40 flex items-center justify-between gap-2 border-b border-zinc-800 bg-zinc-950 px-4 py-3">
+      <p className="text-xs font-semibold text-zinc-500 uppercase tracking-widest">
+        PawFeed Admin
+      </p>
+      <Sheet open={open} onOpenChange={setOpen}>
+        <SheetTrigger render={<Button variant="ghost" size="icon-sm" />}>
+          <Menu className="h-5 w-5" />
+          <span className="sr-only">Menü öffnen</span>
+        </SheetTrigger>
+        <SheetContent
+          side="left"
+          className="flex flex-col gap-1 border-zinc-800 bg-zinc-950 py-6 px-4 text-zinc-100"
+        >
+          <SheetHeader className="p-0 mb-3">
+            <SheetTitle className="text-xs font-semibold text-zinc-500 uppercase tracking-widest">
+              PawFeed Admin
+            </SheetTitle>
+          </SheetHeader>
+          {nav.map(({ href, label, icon }) => (
+            <SheetClose
+              key={href}
+              render={
+                <Link
+                  href={href}
+                  className="flex items-center gap-2.5 px-3 py-2 rounded-lg text-sm text-zinc-300 hover:bg-zinc-800 hover:text-zinc-100 transition-colors"
+                />
+              }
+            >
+              {icon}
+              {label}
+            </SheetClose>
+          ))}
+          <div className="mt-auto pt-3 border-t border-zinc-800">
+            <SheetClose
+              render={
+                <Link
+                  href="/feed"
+                  className="flex items-center gap-2.5 px-3 py-2 rounded-lg text-sm text-zinc-400 hover:bg-zinc-800 hover:text-zinc-100 transition-colors"
+                />
+              }
+            >
+              <ArrowLeft className="h-4 w-4 shrink-0" />
+              Zurück
+            </SheetClose>
+          </div>
+        </SheetContent>
+      </Sheet>
+    </div>
+  );
+}