feat: 添加管理员权限管理功能，更新 AdminUser 模型以支持权限加载，扩展 API 路由以管理后台用户及其权限

app/Http/Controllers/Api/V1/Admin/User/AdminUserPermissionSyncController.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace App\Http\Controllers\Api\V1\Admin\User;
+
+use App\Http\Controllers\Controller;
+use App\Models\AdminPermission;
+use App\Models\AdminUser;
+use App\Support\ApiResponse;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+
+/** PUT /api/v1/admin/admin-users/{admin_user}/permissions */
+final class AdminUserPermissionSyncController extends Controller
+{
+    public function __invoke(Request $request, AdminUser $admin_user): JsonResponse
+    {
+        /** @var array{permission_slugs:list<string>} $data */
+        $data = validator($request->all(), [
+            'permission_slugs' => ['required', 'array'],
+            'permission_slugs.*' => ['string', 'max:128', 'distinct', 'exists:admin_permissions,slug'],
+        ])->validate();
+
+        $slugs = array_values(array_unique($data['permission_slugs']));
+        $permissionIds = AdminPermission::query()
+            ->whereIn('slug', $slugs)
+            ->pluck('id')
+            ->all();
+
+        $admin_user->permissions()->sync($permissionIds);
+        $admin_user->load(['roles.permissions', 'permissions']);
+
+        return ApiResponse::success([
+            'id' => (int) $admin_user->id,
+            'username' => $admin_user->username,
+            'nickname' => $admin_user->name,
+            'roles' => $admin_user->adminRoleSlugs(),
+            'direct_permissions' => $admin_user->permissions
+                ->pluck('slug')
+                ->filter(static fn ($slug): bool => is_string($slug) && $slug !== '')
+                ->values()
+                ->all(),
+            'effective_permissions' => $admin_user->adminPermissionSlugs(),
+        ]);
+    }
+}