feat: MNG → DEV 자동 로그인 API 구현

- login_tokens 테이블 마이그레이션 생성
- LoginToken 모델 생성 (One-Time Token 관리)
- POST /api/v1/token-login 엔드포인트 추가
- 토큰 검증 후 access_token 발급, 1회용 토큰 삭제

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

database/migrations/2025_12_20_132721_create_login_tokens_table.php

@@ -0,0 +1,42 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * MNG → DEV 자동 로그인용 One-Time Token 테이블
+     */
+    public function up(): void
+    {
+        Schema::create('login_tokens', function (Blueprint $table) {
+            $table->id();
+            $table->unsignedBigInteger('user_id')->comment('사용자 ID');
+            $table->string('token', 64)->unique()->comment('One-Time Token (64자)');
+            $table->timestamp('expires_at')->comment('만료 시간');
+            $table->timestamps();
+
+            // 인덱스
+            $table->index('token');
+            $table->index('expires_at');
+
+            // 외래키 (users 테이블과 연결)
+            $table->foreign('user_id')
+                ->references('id')
+                ->on('users')
+                ->cascadeOnDelete();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('login_tokens');
+    }
+};