feat: add custom 404 error page with animated background and navigation links

shop/app/not-found.tsx

@@ -0,0 +1,90 @@
+'use client'
+
+import Link from 'next/link'
+import { motion } from 'framer-motion'
+import { AsciiShaderBackground } from '@/components/AsciiShaderBackground'
+import { ArrowLeft, Home } from 'lucide-react'
+import { Button } from '@/components/ui/button'
+
+export default function NotFound() {
+  return (
+    <div className="min-h-screen bg-transparent text-slate-100 overflow-hidden relative selection:bg-blue-500/30 selection:text-blue-200">
+      <AsciiShaderBackground />
+
+      <div className="relative z-10 flex flex-col items-center justify-center min-h-screen px-4">
+        <motion.div
+          initial={{ opacity: 0, y: 30 }}
+          animate={{ opacity: 1, y: 0 }}
+          transition={{ duration: 0.6, ease: [0.25, 0.1, 0.25, 1] }}
+          className="text-center space-y-8 max-w-lg"
+        >
+          {/* Große 404 */}
+          <motion.h1
+            initial={{ opacity: 0, scale: 0.8 }}
+            animate={{ opacity: 1, scale: 1 }}
+            transition={{ duration: 0.8, delay: 0.1, type: 'spring', stiffness: 100 }}
+            className="text-[10rem] md:text-[14rem] font-black leading-none tracking-tighter bg-gradient-to-b from-white via-slate-300 to-slate-600 bg-clip-text text-transparent select-none"
+          >
+            404
+          </motion.h1>
+
+          {/* Beschreibung */}
+          <motion.div
+            initial={{ opacity: 0, y: 10 }}
+            animate={{ opacity: 1, y: 0 }}
+            transition={{ duration: 0.5, delay: 0.3 }}
+            className="space-y-3"
+          >
+            <h2 className="text-2xl md:text-3xl font-bold text-white">
+              Seite nicht gefunden
+            </h2>
+            <p className="text-slate-400 text-sm md:text-base leading-relaxed max-w-md mx-auto">
+              Die angeforderte Seite existiert nicht oder wurde verschoben.
+            </p>
+          </motion.div>
+
+          {/* Buttons */}
+          <motion.div
+            initial={{ opacity: 0, y: 10 }}
+            animate={{ opacity: 1, y: 0 }}
+            transition={{ duration: 0.5, delay: 0.5 }}
+            className="flex flex-col sm:flex-row items-center justify-center gap-3 pt-4"
+          >
+            <Button
+              asChild
+              size="lg"
+              className="h-12 px-8 text-base gap-2 bg-gradient-to-r from-blue-600 to-sky-500 hover:from-blue-500 hover:to-sky-400 border-0 shadow-[0_0_20px_rgba(56,189,248,0.25)] hover:shadow-[0_0_30px_rgba(56,189,248,0.4)] transition-all"
+            >
+              <Link href="/">
+                <Home className="w-4 h-4" />
+                Zur Startseite
+              </Link>
+            </Button>
+            <Button
+              asChild
+              variant="ghost"
+              size="lg"
+              className="h-12 px-8 text-base gap-2 text-slate-400 hover:text-white border border-white/10 hover:border-white/20 hover:bg-white/5"
+              onClick={() => typeof window !== 'undefined' && window.history.back()}
+            >
+              <button type="button">
+                <ArrowLeft className="w-4 h-4" />
+                Zurück
+              </button>
+            </Button>
+          </motion.div>
+
+          {/* Subtle info */}
+          <motion.p
+            initial={{ opacity: 0 }}
+            animate={{ opacity: 1 }}
+            transition={{ duration: 0.5, delay: 0.7 }}
+            className="text-xs text-slate-600 pt-8"
+          >
+            Fehlercode 404 · CASPOS Shop
+          </motion.p>
+        </motion.div>
+      </div>
+    </div>
+  )
+}