feat: vanish optimization

[vikashsiwach]

This PR introduces a new is_vanished column on the users table to support a more efficient way of handling NIP-62 (request-to-vanish) checks.

Related Issue

Currently NIP-62 query the events table for active kind-62 records on every check.

Fixes issue #436

Motivation and Context

The relay have to check every pubkey for an active request-to-vanish by querying events.As events volume grows ,this becomes less efficient. So we introduced a is_vanished flag in users table for faster checks.

How Has This Been Tested?

• Build/type check:
  npm run build:check
• Unit tests:
  npm run test:unit (504 passing)

Types of changes

• Non-functional change (docs, style, minor refactor)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my code changes.
• All new and existing tests passed.

[cameri]

Are we missing the code refactor to use the new flag on the users table?

[Copilot]

Pull request overview

Adds a database-level optimization for NIP-62 “request-to-vanish” checks by introducing a persisted users.is_vanished flag and backfilling it from existing kind-62 events, reducing reliance on repeated events table lookups.

Changes:

• Add is_vanished boolean column to the users table (default false, not nullable).
• Backfill is_vanished = true for users with non-deleted kind-62 events and insert missing users rows for pubkeys that have active kind-62 events.

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[vikashsiwach]

Hey @cameri ! I made migration reversible (removed user inserts from events) and optimized backfill query using EXISTS. Also missing users issue is solved by adding lazy hydration for is_vanished

[cameri]

@vikashsiwach Please address conflicts that have surfaced