feat(custom-field): tambahkan fitur custom field

- Menambahkan model CustomField dengan atribut mass assignable.
- Membuat request validation untuk custom field.
- Menambahkan route dan breadcrumb untuk custom field.
- Membuat migration untuk tabel custom_fields.
- Menambahkan export functionality untuk custom field.
- Membuat view untuk menambah dan mengedit custom field.

database/migrations/2025_01_30_082943_create_custom_fields_table.php

@@ -0,0 +1,34 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::create('custom_fields', function (Blueprint $table) {
+            $table->id();
+            $table->string('name');
+            $table->string('type');
+            $table->timestamps();
+            $table->softDeletes();
+
+            $table->unsignedBigInteger('created_by')->nullable();
+            $table->unsignedBigInteger('updated_by')->nullable();
+            $table->unsignedBigInteger('deleted_by')->nullable();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('custom_fields');
+    }
+};