四小时，接通第一个集成。

# 1) 获取 access_token
curl -X POST https://api.mrmeos.com/oauth/token
  -d '{"grant_type":"client_credentials",
       "client_id":"...","client_secret":"..."}'
# => { "access_token":"eyJ...", "expires_in":3600 }

# 2) 查询商品列表（Retail OS · 商品域）
curl https://api.mrmeos.com/v1/retail/products?page_size=20
  -H "Authorization: Bearer eyJ..."
  -H "Idempotency-Key: 9f3a1c2e"  # 写操作必带
# => { "data":[{"id":"prod_001","sku":"SKU-001"}],
#      "next_cursor":"eyJvZmZzZXQiOjIwfQ" }