revert: [attendance] MNG 마이그레이션 정책 변경 되돌림

- MNG 마이그레이션 파일 삭제 (API에서 관리)
- CLAUDE.md DB 아키텍처 규칙 원래대로 복원
- 마이그레이션은 API 프로젝트에서만 관리

database/migrations/2026_02_26_100000_create_attendance_requests_table.php

@@ -1,43 +0,0 @@
-<?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
-    {
-        if (Schema::hasTable('attendance_requests')) {
-            return;
-        }
-
-        Schema::create('attendance_requests', function (Blueprint $table) {
-            $table->id();
-            $table->unsignedBigInteger('tenant_id');
-            $table->unsignedBigInteger('user_id')->comment('신청자');
-            $table->enum('request_type', ['vacation', 'businessTrip', 'remote', 'fieldWork'])->comment('신청 유형');
-            $table->date('start_date');
-            $table->date('end_date');
-            $table->text('reason')->nullable()->comment('사유');
-            $table->enum('status', ['pending', 'approved', 'rejected'])->default('pending');
-            $table->unsignedBigInteger('approved_by')->nullable()->comment('승인자');
-            $table->timestamp('approved_at')->nullable();
-            $table->text('reject_reason')->nullable()->comment('반려 사유');
-            $table->json('json_details')->nullable()->comment('반차 구분 등 추가 정보');
-            $table->timestamps();
-            $table->softDeletes();
-
-            $table->foreign('tenant_id')->references('id')->on('tenants')->cascadeOnDelete();
-            $table->foreign('user_id')->references('id')->on('users')->cascadeOnDelete();
-
-            $table->index(['tenant_id', 'status']);
-            $table->index(['tenant_id', 'user_id']);
-        });
-    }
-
-    public function down(): void
-    {
-        Schema::dropIfExists('attendance_requests');
-    }
-};