Implement CLI argument parsing with clap and config file loading

- Add Cli struct with clap derive macros for --config, --validate, --allow-wildcard-bind flags
- Config loading: reads TOML, deserializes into StaticConfig + DynamicConfig, validates
- --validate: load, validate, print success/errors, exit 0 or 1
- --allow-wildcard-bind is OR'd with config allow_wildcard_bind field
- Default config path: /etc/reverse-proxy/config.toml
- Version from Cargo.toml via clap
- Unit tests for CLI argument parsing and config loading
- Integration tests for --validate with valid/invalid config and --allow-wildcard-bind

src/lib.rs

@@ -1,4 +1,5 @@
 pub mod admin;
+pub mod cli;
 pub mod config;
 pub mod health;
 pub mod logging;