Description:
Currently, the relay checks for an active NIP-62(kind:62) vanish request by querying the events table.
If the number of events grows ,this will not be a good practice to scale and will need a additional query.
To be more efficient , we can add a flag to users table (e.g. is_vanished) .

Solution:

• Add a boolean flag (is_vanished) to the users table.
• Set this flag when a kind:62 event is processed.
• Use this flag for vanish checks instead of querying events table.

Benefit:

• Faster lookups (no event table scan)
• Simpler logic for checking vanish state
• Better scalability as event volume grows

Additional context
Optimize the performance of NIP-62 in PR #418