Remove axios, lodash, is-ip, url-join; use native alternatives

BREAKING CHANGE: Requires Node.js >= 18 (for native fetch).
CacheConfig.maxAge renamed to CacheConfig.ttl (from lru-cache v11).
Version bumped to 3.0.0.

- Replace axios with native fetch (zero-dep HTTP)
- Replace lodash/isString and lodash/isArray with typeof/Array.isArray
- Replace is-ip with Node built-in net.isIP()
- Replace url-join with URL constructor
- Mock all HTTP calls in tests (no API key required for CI)
- Remove dotenv-cli (tests no longer need env vars)
- Runtime deps reduced from 6 to 2 (lru-cache, tslib)

https://claude.ai/code/session_01UabaLo3R3sXovyxaZo2yCF

Author: claude