Async private key - server side generation

Current implementation sends masterPassword to backend in order to generate the keys, but when decrypting on frontend the encrypted private key is sent along with iv and decrypted client side.

Potential security risk of having to send masterPassword through unsure medium.
Ideally keys should be generated & encrypted client side - then sent over to backend.

查看目前的金鑰產生 endpoint 和客戶端解密邏輯。了解 masterPassword 目前是如何傳送的，以及私鑰加密/解密發生的位置。目標是在發送到後端前將金鑰生成和加密移到前端。檢查現有的 API 路由和 Strapi 的服務中的加密作業。

由索引模型根據 Issue 內容生成。