Add httpserver package: TLS HTTP server with chi

- Server wrapping chi.Mux + http.Server with TLS 1.3 minimum
- ListenAndServeTLS and graceful Shutdown
- LoggingMiddleware (method, path, status, duration, remote)
- StatusWriter for status code capture in middleware
- WriteJSON and WriteError helpers
- 8 tests

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

go.sum

@@ -1,5 +1,7 @@
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