feat: custom halaman error 403 & 404 premium

- 403: icon shield, merah soft, pesan dinamis
- 404: icon map, amber soft
- Tombol Kembali + Dashboard
- Dekorasi dots
- Menggunakan layout app (navbar + sidebar tetap)

resources/views/errors/404.blade.php

@@ -0,0 +1,36 @@
+@extends('layouts.app')
+
+@section('title', 'Halaman Tidak Ditemukan')
+
+@section('content')
+<div class="min-h-[70vh] flex items-center justify-center">
+    <div class="text-center max-w-md mx-auto px-4">
+        <div class="mx-auto w-20 h-20 rounded-2xl bg-gradient-to-br from-amber-50 to-amber-100 border border-amber-200 flex items-center justify-center shadow-sm mb-6">
+            <i class="fa-solid fa-map text-3xl text-amber-400"></i>
+        </div>
+
+        <div class="text-7xl font-black text-amber-200 tracking-tight mb-2">404</div>
+        <h1 class="text-xl font-bold text-gray-900 mb-2">Halaman Tidak Ditemukan</h1>
+        <p class="text-sm text-gray-500 leading-relaxed mb-8">Halaman yang Anda cari mungkin telah dipindah atau tidak tersedia.</p>
+
+        <div class="flex items-center justify-center gap-3">
+            <a href="{{ url()->previous() !== url()->current() ? url()->previous() : route('dashboard') }}"
+                class="inline-flex items-center gap-2 px-5 py-2.5 text-sm font-semibold text-gray-700 bg-white border border-gray-200 rounded-xl hover:bg-gray-50 transition shadow-sm">
+                <i class="fa-solid fa-arrow-left text-xs"></i>
+                Kembali
+            </a>
+            <a href="{{ route('dashboard') }}"
+                class="inline-flex items-center gap-2 px-5 py-2.5 text-sm font-semibold text-white bg-blue-600 rounded-xl hover:bg-blue-700 transition shadow-sm">
+                <i class="fa-solid fa-house text-xs"></i>
+                Dashboard
+            </a>
+        </div>
+
+        <div class="mt-12 flex items-center justify-center gap-1.5">
+            <span class="w-1.5 h-1.5 rounded-full bg-amber-200"></span>
+            <span class="w-1.5 h-1.5 rounded-full bg-amber-300"></span>
+            <span class="w-1.5 h-1.5 rounded-full bg-amber-400"></span>
+        </div>
+    </div>
+</div>
+@endsection