- Add request_validator.h/c with comprehensive authentication system
- Implement pluggable database backend interface (SQLite default)
- Add priority-based rule evaluation engine with caching
- Support pubkey whitelist/blacklist, hash blacklist, MIME restrictions
- Add new authentication error codes to nostr_common.h
- Include request_validator.h in nostr_core.h
- Update build.sh to compile request_validator.c
- Designed for shared use between ginxsom and c-relay projects