Enable runtime-configurable HTTPS for smartdns-ui and remove compile-time TLS gating

[PikuZheng]

Motivation

• Make HTTPS support configurable at runtime via an https_port setting instead of being controlled by a compile feature and URL scheme.

Description

• Add https_port to HttpServerConfig, load it from server config and command-line (--https-port), and expose it in settings_map.
• Replace compile-time feature gating for TLS with runtime logic that creates a rustls TlsAcceptor and a separate HTTPS TcpListener when https_port > 0, accepting TLS connections concurrently with HTTP.
• Remove cfg_if usage and make tokio-rustls/rustls-pemfile available unconditionally by changing Cargo.toml so TLS dependencies are no longer optional and the https feature no longer maps to them.
• Update argument parsing in plugin.rs to accept --https-port and minor whitespace/format cleanup.

Testing

• Built the smartdns-ui crate with cargo build -p smartdns-ui and the build completed successfully.
• Ran the crate test suite with cargo test -p smartdns-ui and all tests passed.

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Codex Task