Add secure nsec key generation and encryption for web UI (v0.36.7)

- Add nsec-crypto.js library with Argon2id+AES-GCM encryption
- Generate new nsec keys using secure system entropy
- Encrypt nsec with password (~3 sec Argon2id derivation in Web Worker)
- Add unlock flow for returning users with encrypted keys
- Add deriving modal with live timer during key derivation
- Auto-create default profile for new users with ORLY logo avatar
- Fix NIP-42 auth race condition in websocket-auth.js
- Improve header user profile display (avatar fills height, no truncation)
- Add instant light/dark theme colors in HTML head
- Add background box around username/nip05 in settings drawer
- Update CLAUDE.md with nsec-crypto library documentation

Files modified:
- app/web/src/nsec-crypto.js: New encryption library
- app/web/src/LoginModal.svelte: Key gen, encryption, unlock UI
- app/web/src/nostr.js: Default profile creation
- app/web/src/App.svelte: Header and drawer styling
- app/web/public/index.html: Instant theme colors
- CLAUDE.md: Library documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pkg/version/version

@@ -1 +1 @@
-v0.36.6
+v0.36.7