[WEB-5040] feat: admin react-router migration (#7922)

apps/admin/app/components/404.tsx

@@ -0,0 +1,34 @@
+import React from "react";
+import { Link } from "react-router";
+// ui
+import { Button } from "@plane/propel/button";
+// images
+import Image404 from "@/app/assets/images/404.svg?url";
+
+const PageNotFound = () => (
+  <div className={`h-screen w-full overflow-hidden bg-custom-background-100`}>
+    <div className="grid h-full place-items-center p-4">
+      <div className="space-y-8 text-center">
+        <div className="relative mx-auto h-60 w-60 lg:h-80 lg:w-80">
+          <img src={Image404} alt="404 - Page not found" className="h-full w-full object-contain" />
+        </div>
+        <div className="space-y-2">
+          <h3 className="text-lg font-semibold">Oops! Something went wrong.</h3>
+          <p className="text-sm text-custom-text-200">
+            Sorry, the page you are looking for cannot be found. It may have been removed, had its name changed, or is
+            temporarily unavailable.
+          </p>
+        </div>
+        <Link to="/general/">
+          <span className="flex justify-center py-4">
+            <Button variant="neutral-primary" size="md">
+              Go to general settings
+            </Button>
+          </span>
+        </Link>
+      </div>
+    </div>
+  </div>
+);
+
+export default PageNotFound;