feat(nwcp): add NIP-44 v2 encryption

[satwise]

Summary

• advertise nip44_v2 nip04 in the NIP-47 kind-13194 info event
• decrypt NIP-44 v2 request events when the request includes ["encryption", "nip44_v2"]
• encrypt responses with the same scheme requested by the client while preserving NIP-04 fallback
• add coverage for the published NIP-44 vector and NIP-44 request/response handling

Closes #41

Testing

• uvx ruff check nwcp.py tests/unit/test_nwcp.py
• uvx black --check nwcp.py tests/unit/test_nwcp.py
• python -m py_compile nwcp.py tests/unit/test_nwcp.py
• direct NIP-44 harness with real pynostr, coincurve==20.0.0, cryptography, loguru, and websockets plus lightweight LNbits stubs

Note: full uv run pytest is blocked in this Windows environment because LNbits pulls uvloop, which does not support Windows.

[Copilot]

Pull request overview

This PR adds NIP-44 v2 support to NWCServiceProvider so the provider can advertise, decrypt requests, and encrypt responses using nip44_v2, while preserving nip04 as a fallback for compatibility with existing clients.

Changes:

• Add NIP-44 v2 encrypt/decrypt implementation (HKDF-SHA256 + ChaCha20 + HMAC-SHA256) and route request/response handling based on an encryption tag.
• Advertise supported encryptions (nip44_v2 nip04) in the kind-13194 info event.
• Add unit tests for the published NIP-44 v2 vector and for end-to-end request/response handling using nip44_v2.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
nwcp.py	Implements NIP-44 v2 crypto, adds encryption negotiation via tags, and updates info event advertisement + response encryption behavior.
tests/unit/test_nwcp.py	Adds vector test and async handling tests to cover NIP-44 v2 request decryption and response encryption/tagging.

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