Remove unused log_rate_limit! and log_config_reload! macros,
format_event_fields() function, ProxyError::NotFound/BadRequest/
PayloadTooLarge/UpstreamTls variants, build_multi_domain_server_config(),
SniCertResolver struct, and dead test helper methods. Gate
AcmeTlsConfig::directory_url() and KvVisitor with #[cfg(test)].
- Add [lib] target to enable integration test imports
- Add rcgen and reqwest dev-dependencies for TLS and HTTP test helpers
- Create src/config/test_fixtures.rs with test_static_config() and test_dynamic_config()
- Create tests/ with integration tests, HTTP test helper (TestUpstream), and TLS test helper (SelfSignedCert)
- Add Clone derives to StaticConfig and related structs for test fixture construction
- All existing tests continue to pass
