feat(dns): parallel queries, LRU cache, retry with backoff

- Query A and AAAA records in parallel for DnsRecordType::ANY
- Add LRU cache eviction (max 1000 entries)
- Retry UDP queries with exponential backoff (1s, 2s)
- Add benchmarking scripts (excluded from installs)

/claude

perf: optimize single-socket accept with phasync::readable()

- Use phasync::readable() instead of phasync::select() for single-socket servers
- Add configurable read/write buffer sizes (default: 0 for zero-copy)
- Use PHP_FLOAT_MAX timeout to prevent server timeout while waiting
- ~30% performance improvement (2400 -> 3150 rps)

/claude

unix:// fix 2

Fixed issue with unix socket addresses

Added tests and documentation

Initial commit