v7: options-object API, request cancellation, strict TypeScript

[laurentpellegrino]

Summary

The v7 modernization: reshapes the public API to idiomatic TypeScript while keeping every 6.x call form working as a deprecated alias with identical behavior.

• Options-object construction: new IpregistryClient({ apiKey, baseUrl: 'eu', cache, maxRetries, timeout, ... }) replaces the IpregistryConfigBuilder pattern (builder still works, marked deprecated). The plain API-key-string form remains non-deprecated.
• Per-call LookupOptions: client.lookupIp(ip, { fields, hostname, params, signal }) replaces variadic IpregistryOptions.filter(...) style options (also still working, deprecated). Cache keys are identical between the two forms, so mixed usage shares the cache.
• Request cancellation: every lookup accepts { signal: AbortSignal }. Aborting cancels the in-flight fetch, pending retries and their backoff waits (with AbortSignal.any and a fallback for Node < 20.3), and pending batch chunks. Error messages mirror the Go client (Request cancelled, Request cancelled during retry backoff).
• parseUserAgents accepts an array; the variadic form is deprecated.
• Full strict TypeScript: noImplicitAny enabled; IpregistryCache<V> is generic with a new IpregistryCacheValue type; @types/chai added for the test suite.
• README examples migrated to the new API; CHANGELOG carries a migration table.

Compatibility

All 46 pre-existing tests pass unchanged against this branch, plus 8 new tests for the v7 surface (54 total). Runtime smoke tests pass on Node and workerd; @arethetypeswrong/cli reports no problems.

Version is bumped to 7.0.0 on the branch; releasing stays a manual gh workflow run release.yaml -f version=7.0.0 after merge.