Resolve client IP from the socket peer address as a fallback

[bartes]

The client IP is now resolved from the connection's peer address when no X-Forwarded-For or Remote-Addr header is present, so direct and localhost requests carry a context.ip instead of none.

Changes

• IPsExtractService.call accepts an optional remoteAddress and surfaces it as remote-addr only when that header is absent. It participates in extraction with the existing precedence (after X-Forwarded-For), trusted-proxy filtering, trustedProxyDepth, and trustProxyChain. An existing remote-addr header is preserved, and custom ipHeaders that exclude remote-addr ignore it.
• ContextGetDefaultService derives the value from the request connection across frameworks: socket.remoteAddress, then connection.remoteAddress, then info.remoteAddress (raw Node IncomingMessage, Express, Fastify, Koa, Next, Hapi).
• Added a shared CastleRequest type for the request shape consumed by the context services.
• README documents the socket fallback under Client IP detection.

The third IPsExtractService.call argument is optional and the fallback only applies when no IP header yields a value, so existing behavior is unchanged.

[bartes]

Closing for now — the localhost case is handled in the example app instead. Keeping the branch around in case we revisit SDK-level autodetection.