feat: Add Nip42 handler

[Anshumancanrock]

Description

Second PR for NIP-42 (follows #622). This one wires everything up so the adapter now sends a challenge on connect and there's a handler to verify the client's AUTH response.

• WebSocketAdapter generates a random challenge on connect and sends ["AUTH", <challenge>]
• new AuthMessageHandler verifies kind 22242 events (checks id, sig, timestamp, challenge tag, relay domain)
• on success the pubkey gets stored in a per-connection set, cleared on disconnect
• kind 22242 is blocked from the normal EVENT pipeline so it can't hit storage
• messageHandlerFactory routes AUTH messages to the new handler
• extended IWebSocketAdapter with getChallenge(), getAuthenticatedPubkeys(), addAuthenticatedPubkey()

Related Issue

Closes #619

Motivation and Context

With the types from #622 in place, this wires up the actual auth flow so connections can be tied to a pubkey. Sets things up for NIP-70 protected events next.

How Has This Been Tested?

Added 20 new tests across the handler, adapter and factory specs.

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.
• I added a changeset, or this is docs-only and I added an empty changeset.
• All new and existing tests passed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 44034c7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
nostream	Minor

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[coveralls]

coverage: 65.411% (+0.3%) from 65.119% — Anshumancanrock:nip42-handler into cameri:main