Add src/app/not-found.tsx

src/app/not-found.tsx

@@ -0,0 +1,59 @@
+"use client";
+
+import Link from "next/link";
+import { AlertCircle, Home, Search } from "lucide-react";
+
+export default function NotFound() {
+  return (
+    <div className="min-h-screen flex items-center justify-center px-4 py-12 bg-gradient-to-br from-background to-card">
+      <div className="max-w-md w-full text-center">
+        <div className="flex justify-center mb-6">
+          <AlertCircle size={64} className="text-primary-cta opacity-80" />
+        </div>
+        
+        <h1 className="text-5xl font-bold text-foreground mb-2">404</h1>
+        <h2 className="text-2xl font-semibold text-foreground mb-4">Sayfa Bulunamadı</h2>
+        
+        <p className="text-gray-600 mb-8">
+          Aradığınız sayfa taşınmış, silinmiş veya hiç var olmayabilir. Lütfen aşağıdaki bağlantılardan birini kullanarak geri dönün.
+        </p>
+
+        <div className="flex flex-col gap-3">
+          <Link
+            href="/"
+            className="inline-flex items-center justify-center gap-2 px-6 py-3 bg-primary-cta text-white rounded-lg hover:opacity-90 transition-opacity font-semibold"
+          >
+            <Home size={18} />
+            Ana Sayfaya Dön
+          </Link>
+          
+          <Link
+            href="/teachers"
+            className="inline-flex items-center justify-center gap-2 px-6 py-3 bg-card border border-border text-foreground rounded-lg hover:bg-background transition-colors font-semibold"
+          >
+            <Search size={18} />
+            Öğretmenleri Gözat
+          </Link>
+        </div>
+
+        <div className="mt-12 p-6 bg-card rounded-lg border border-border">
+          <h3 className="font-semibold text-foreground mb-3">Başka ne yapabiliriz?</h3>
+          <ul className="text-sm text-gray-600 space-y-2 text-left">
+            <li className="flex items-start gap-2">
+              <span className="text-primary-cta mt-1">•</span>
+              <span>Arama yardımı için destek ekibimizle iletişime geçin</span>
+            </li>
+            <li className="flex items-start gap-2">
+              <span className="text-primary-cta mt-1">•</span>
+              <span>Ana menüyü kullanarak platformda gezin</span>
+            </li>
+            <li className="flex items-start gap-2">
+              <span className="text-primary-cta mt-1">•</span>
+              <span>İstenilen dersi veya konuyu seçin</span>
+            </li>
+          </ul>
+        </div>
+      </div>
+    </div>
+  );
+}