ZeroTalk clone published two topics at a time and one was lost

### Step 1: Please describe your environment

* ZeroNet version: 4496
* Operating system: W10
* Web browser: FF

### Step 2: Describe the problem:

On ZeroTalk clone i was publishing new topics. On my instance it sometimes takes more than 10 seconds for the newly submitted discussion thread or editted the post to publish into database (or into .json file?) And this time it took longer and happened that there was two new threads being submitted at a time. And apparently the later submitted thread somehow overwritten the previous one, because i am unable to find one of the threads and i also do not know how i can recover the text that was submitted.

I spent around 30 minutes writing that topic post and it contained valuable information. Please can you give this a priority?

まず、報告された Windows 10 と Firefox の環境で、ZeroTalk クローンにほぼ同時に 2 件のトピックを送信するケースを再現します。送信されたディスカッションがデータベースまたは JSON ファイルにどのように永続化されるかを追跡し、なぜ一方のエントリが消えるのかを特定します。並行して公開した後も両方のトピックを復元でき、このケースのリグレッションチェックがある状態を完了とします。

索引モデルが issue の本文から書いたものです。