Don't drop file history after all clients disconnect

[PotentialStyx]

When all clients detach (happens on disconnect), a service is shutdown. If the db is disabled this will lead to ot channels losing history due to being restarted with no db to retrieve file history from.

Solutions:

• When db is disabled use an in memory version to store file history - Downside file history has to be stored twice (v8 and rust side)
• Never shutdown ot service v8 isolates - Resource usage, when no clients are connected no services should run

[rayhanadev]

E