Initialize Rust project with Cargo, dependencies, and module skeleton

Set up single-binary reverse-proxy project with all core dependencies
(axum, tokio, hyper, tower, rustls, tokio-rustls, rustls-acme, serde,
toml, arc-swap, tracing, tracing-subscriber, rustls-pemfile,
rustls-pki-types, clap, signal-hook, anyhow, thiserror) pinned to exact
versions. Create module skeleton (config, proxy, tls, rate_limit,
logging, admin, health, shutdown) matching architecture spec.

src/main.rs

@@ -0,0 +1,12 @@
+mod admin;
+mod config;
+mod health;
+mod logging;
+mod proxy;
+mod rate_limit;
+mod shutdown;
+mod tls;
+
+fn main() {
+    tracing::info!("reverse-proxy starting");
+}