Implement soft delete for rooms and messages

[VictrixHominum]

Which feature are you enhancing?
Data deletion and recovery capabilities

Why is this required?
Hard deletion of rooms and messages creates risk of accidental data loss and makes it impossible to recover from user mistakes. Implementing soft delete will improve data safety while still allowing for eventual permanent deletion.

Any additional context?
This requires schema changes to add deletedAt fields to Chatroom and Message models. All queries need to be modified to filter out soft-deleted records by default. Consider implementing a Prisma middleware to handle this filtering automatically. Add admin interfaces for recovery operations and scheduled jobs for permanent deletion after a configurable period.