feat: implement custom 404 page with NotFound component and navigation options

src/components/NotFound.tsx

@@ -0,0 +1,81 @@
+import React from "react";
+import { Button } from "@/components/ui/button";
+import { Card, CardContent, CardHeader } from "@/components/ui/card";
+import { Home, ArrowLeft, GitBranch, BookOpen, Settings, FileQuestion } from "lucide-react";
+
+export function NotFound() {
+  return (
+    <div className="h-dvh bg-muted/30 flex items-center justify-center p-4">
+      <Card className="w-full max-w-md">
+        <CardHeader className="text-center pb-4">
+          <div className="mx-auto mb-4 h-16 w-16 rounded-full bg-muted flex items-center justify-center">
+            <FileQuestion className="h-8 w-8 text-muted-foreground" />
+          </div>
+          <h1 className="text-3xl font-bold">404</h1>
+          <h2 className="text-xl font-semibold mt-2">Page Not Found</h2>
+          <p className="text-muted-foreground mt-2">
+            The page you're looking for doesn't exist or has been moved.
+          </p>
+        </CardHeader>
+        
+        <CardContent className="space-y-6">
+          {/* Action Buttons */}
+          <div className="flex flex-col gap-3">
+            <Button asChild className="w-full">
+              <a href="/">
+                <Home className="mr-2 h-4 w-4" />
+                Go to Dashboard
+              </a>
+            </Button>
+            <Button variant="outline" className="w-full" onClick={() => window.history.back()}>
+              <ArrowLeft className="mr-2 h-4 w-4" />
+              Go Back
+            </Button>
+          </div>
+
+          {/* Divider */}
+          <div className="relative">
+            <div className="absolute inset-0 flex items-center">
+              <span className="w-full border-t" />
+            </div>
+            <div className="relative flex justify-center text-xs uppercase">
+              <span className="bg-card px-2 text-muted-foreground">or visit</span>
+            </div>
+          </div>
+
+          {/* Quick Links */}
+          <div className="grid grid-cols-3 gap-3">
+            <a 
+              href="/repositories" 
+              className="flex flex-col items-center gap-2 p-3 rounded-md hover:bg-muted transition-colors"
+            >
+              <GitBranch className="h-5 w-5 text-muted-foreground" />
+              <span className="text-xs">Repositories</span>
+            </a>
+            <a 
+              href="/config" 
+              className="flex flex-col items-center gap-2 p-3 rounded-md hover:bg-muted transition-colors"
+            >
+              <Settings className="h-5 w-5 text-muted-foreground" />
+              <span className="text-xs">Config</span>
+            </a>
+            <a 
+              href="/docs" 
+              className="flex flex-col items-center gap-2 p-3 rounded-md hover:bg-muted transition-colors"
+            >
+              <BookOpen className="h-5 w-5 text-muted-foreground" />
+              <span className="text-xs">Docs</span>
+            </a>
+          </div>
+
+          {/* Error Code */}
+          <div className="text-center pt-2">
+            <p className="text-xs text-muted-foreground">
+              Error Code: <code className="font-mono">404_NOT_FOUND</code>
+            </p>
+          </div>
+        </CardContent>
+      </Card>
+    </div>
+  );
+}