feat: implement NIP-17 & NIP-44 v2 for Modern Direct Messages

[CKodidela]

Description

This PR introduces comprehensive support for NIP-17 (Private Direct Messages) and NIP-44 v2 (Encrypted Payloads), establishing the modern standard for secure messaging on Nostr.

Changes included:

• NIP-17 Support:
  • Added new Event Kinds: Seal (13), Direct Message (14), File Message (15), and Gift Wrap (1059).
  • Implemented GiftWrapEventStrategy to handle and validate incoming Gift Wrap events.
  • Added repository-level protections to block direct relay publication of inner events (Kinds 13, 14, 15), mandating they be encrypted inside a Gift Wrap.
• NIP-44 v2 Crypto:
  • Implemented nip44Encrypt and nip44Decrypt functions supporting ChaCha20, HKDF extraction/expansion, and MAC verification as per NIP-44 v2 specifications.
  • Added validateNip44Payload to ensure payloads adhere to the exact format requirements without needing to decrypt them.
• Cleanup:
  • Removed deprecated encryptKind4Event (legacy NIP-04 DM algorithm) from event.ts.
  • Updated package.json to declare NIPs 17 and 44 in supportedNipExtensions.
• Tests:
  • Added extensive unit tests across NIP-44 encryption logic, Event Strategies, and Message Handlers.
  • Resolved sort-imports ESLint violations in multiple handler specs.

Related Issue

Closes #410

Motivation and Context

The Nostr ecosystem is migrating to NIP-17 and NIP-44 v2 for private direct messages because the legacy NIP-04 standard was found to have systemic metadata leaks and weak encryption. This PR adopts the new, much more private standard by actively supporting Gift Wrap events, handling NIP-44 payload validation natively, and safely rejecting any unprotected inner events before they hit the database, ultimately protecting the relay's users.

How Has This Been Tested?

• Added specific unit tests for all NIP-44 v2 crypto functions (key derivation, encryption limits, validation failures).
• Unit tested the newly added helper methods detecting NIP-17 inner events.
• Covered EventMessageHandler with tests to ensure it correctly blocks standard publications of Kinds 13, 14, and 15 without a wrapper.
• Validated NIP-59/NIP-17 structural integrity (p tags limitations) within GiftWrapEventStrategy.spec.ts.
• Automatically passed standard verification layers, including fixing prior ESLint violations in test packages, and successfully executed npm run test:unit.

Screenshots (if appropriate):

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. (Updated supportedNipExtensions in package metadata)
• I have read the CONTRIBUTING document.
• I have added tests to cover my code changes.
• All new and existing tests passed.

[CKodidela]

@phoenix-server @cameri This pr is ready for review and checks
Local checks including lint, unit passed.

[Copilot]

Pull request overview

Adds modern Nostr direct-message support by introducing NIP-17 event kinds and handling for Gift Wrap events, alongside a new NIP-44 v2 encryption/decryption utility and associated unit tests.

Changes:

• Added NIP-44 v2 crypto utilities (nip44Encrypt, nip44Decrypt, validateNip44Payload, getConversationKey) plus test vectors and round-trip tests.
• Introduced NIP-17-related event kinds (13/14/15/1059), helpers, and a GiftWrapEventStrategy to validate/persist/broadcast Gift Wrap events.
• Blocked direct publication of NIP-17 inner kinds (13/14/15) in EventMessageHandler, and updated relay metadata (supportedNips).

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
test/unit/utils/nip44.spec.ts	Adds NIP-44 v2 test vectors, round-trip coverage, and validation tests.
test/unit/utils/event.spec.ts	Adds unit tests for new NIP-17 kind helper predicates.
test/unit/handlers/event-strategies/gift-wrap-event-strategy.spec.ts	Tests Gift Wrap strategy validation and persistence/broadcast behavior.
test/unit/handlers/event-message-handler.spec.ts	Tests blocking of direct publication of kinds 13/14/15.
src/utils/nip44.ts	Implements NIP-44 v2 key derivation, encryption/decryption, and payload structural validation.
src/utils/event.ts	Removes legacy kind-4 encrypt helper and adds NIP-17 kind helper predicates.
src/handlers/event-strategies/gift-wrap-event-strategy.ts	Adds strategy for validating and storing Gift Wrap (1059) events.
src/handlers/event-message-handler.ts	Blocks direct publication of NIP-17 inner event kinds (13/14/15).
src/factories/event-strategy-factory.ts	Routes kind 1059 events to GiftWrapEventStrategy.
src/constants/base.ts	Adds NIP-17 event kinds (13/14/15) and Gift Wrap kind (1059).
package.json	Declares support for NIPs 17 and 44 in relay metadata.
package-lock.json	Updates lockfile entries (including dependency spec normalization).

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[CKodidela]

@cameri I've resolved copilot suggestions, This PR is now ready for review
Thanks