feat: 新增採購單發票欄位、更新 SearchableSelect 樣式與搜尋門檻至 10 個項目

database/migrations/2026_01_09_095718_add_invoice_fields_to_purchase_orders_table.php

@@ -0,0 +1,30 @@
+<?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::table('purchase_orders', function (Blueprint $table) {
+            $table->string('invoice_number', 11)->nullable()->comment('發票號碼 (格式: AB-12345678)');
+            $table->date('invoice_date')->nullable()->comment('發票日期');
+            $table->decimal('invoice_amount', 12, 2)->nullable()->comment('發票金額');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('purchase_orders', function (Blueprint $table) {
+            $table->dropColumn(['invoice_number', 'invoice_date', 'invoice_amount']);
+        });
+    }
+};