feat: API 폐기 후보 관리 테이블 마이그레이션 추가

- admin_api_deprecations 테이블 생성
- 상태: candidate, scheduled, deprecated, removed

database/migrations/2025_12_18_170000_create_admin_api_deprecations_table.php

@@ -0,0 +1,33 @@
+<?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('admin_api_deprecations', function (Blueprint $table) {
+            $table->id();
+            $table->string('endpoint', 500)->comment('API 엔드포인트');
+            $table->string('method', 10)->comment('HTTP 메서드');
+            $table->enum('status', ['candidate', 'scheduled', 'deprecated', 'removed'])
+                ->default('candidate')
+                ->comment('상태: 후보, 예정, 폐기됨, 삭제됨');
+            $table->text('reason')->nullable()->comment('폐기 사유');
+            $table->date('scheduled_date')->nullable()->comment('폐기 예정일');
+            $table->date('deprecated_date')->nullable()->comment('실제 폐기일');
+            $table->foreignId('created_by')->nullable()->constrained('users')->nullOnDelete();
+            $table->timestamps();
+
+            $table->unique(['endpoint', 'method']);
+            $table->index('status');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('admin_api_deprecations');
+    }
+};