feat:미수금(receivables) 테이블 마이그레이션 추가

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

database/migrations/2026_02_04_222005_create_receivables_table.php

@@ -0,0 +1,35 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('receivables', function (Blueprint $table) {
+            $table->id();
+            $table->unsignedBigInteger('tenant_id');
+            $table->string('customer_name', 100);
+            $table->string('invoice_no', 50);
+            $table->date('issue_date');
+            $table->date('due_date')->nullable();
+            $table->string('category', 50)->default('서비스');
+            $table->bigInteger('amount')->default(0);
+            $table->bigInteger('collected_amount')->default(0);
+            $table->string('status', 20)->default('outstanding'); // outstanding, partial, collected, overdue
+            $table->string('description', 255)->nullable();
+            $table->text('memo')->nullable();
+            $table->timestamps();
+            $table->softDeletes();
+            $table->index(['tenant_id', 'status']);
+            $table->index(['tenant_id', 'due_date']);
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('receivables');
+    }
+};