cnats: NATS-native chat with Leptos SSR and Kanidm SSO

Initial import plus deployment packaging: multi-stage Dockerfile
(cargo-leptos build -> debian-slim runtime), .dockerignore, and a
dev-only docker-compose (app + local NATS). Production deployment
lives in the infrastructure repo.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/lib.rs

@@ -0,0 +1,13 @@
+pub mod app;
+pub mod auth;
+pub mod chat;
+
+#[cfg(feature = "ssr")]
+pub mod server;
+
+#[cfg(feature = "hydrate")]
+#[wasm_bindgen::prelude::wasm_bindgen]
+pub fn hydrate() {
+    console_error_panic_hook::set_once();
+    leptos::mount::hydrate_body(app::App);
+}