v2.0.0 of nostr

Pure-Dart Nostr protocol library. Events, signing, NIP-44 encryption, gift wrap, and 35+ NIPs. Transport-agnostic, Flutter Web compatible. Changelog excerpt: First major rewrite since v1.5.0. The library is now pure-protocol (no transport / WebSocket dependency), Flutter Web compatible, and spec-aligned against the upstream nostr-protocol/nipsmaster. NIP-04 plaintext DMs are gone, every NIP has typed parse output, and all crypto runs through Schnorr/ Encryption(no direct bip340). ### Breaking Changes NIP-04 removed— Use Nip17/ DirectMessage(NIP-17 over NIP-59 gift wrap) instead. **Parameter privkeyrenamed to secretKey**across t[...]