Add SSEBroker type that manages SSE client connections and broadcasts
events to subscribed clients. Clients connect via GET /events and
optionally filter by channel with ?channel=<name>. Includes Publish,
ClientCount, and Drain methods for event broadcasting and lifecycle
management.
Co-Authored-By: Virgil <virgil@lethean.io>
Engine manages route groups and builds a Gin-based HTTP handler.
New() accepts functional options (WithAddr). Handler() builds a fresh
Gin engine with Recovery middleware and /health endpoint. Serve()
starts the server and performs graceful shutdown on context cancellation.
Co-Authored-By: Virgil <virgil@lethean.io>
