feat: 添加 Laravel Sanctum 支持，增强管理员 API 鉴权，更新相关中间件与路由配置

app/Http/Controllers/Api/V1/Admin/Auth/CaptchaController.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace App\Http\Controllers\Api\V1\Admin\Auth;
+
+use App\Services\AdminCaptchaService;
+use App\Support\ApiResponse;
+use Illuminate\Http\JsonResponse;
+
+/**
+ * GET /api/v1/admin/auth/captcha
+ *
+ * 返回一次性验证码 Key 与 SVG（Base64 便于前台直接赋值给 img.src）。
+ */
+final class CaptchaController
+{
+    public function __invoke(AdminCaptchaService $captcha): JsonResponse
+    {
+        $payload = $captcha->create();
+
+        return ApiResponse::success([
+            'captcha_key' => $payload['captcha_key'],
+            'image_base64' => $payload['image_base64'],
+        ]);
+    }
+}