fix: HTTPS with self-signed cert for Web Crypto API support

Browsers disable crypto.subtle on non-localhost HTTP. The frontend server now
generates a self-signed TLS cert at startup and serves over HTTPS by default
(FRONTEND_TLS=true). FRONTEND_TLS=0 disables it for localhost dev.

Added axum-server (tls-rustls) + rcgen deps to the frontend-server crate.

web/frontend-server/Cargo.toml

@@ -12,3 +12,5 @@ axum = "0.7"
 tokio = { version = "1", features = ["full"] }
 tower-http = { version = "0.5", features = ["fs", "trace"] }
 reqwest = { version = "0.12", features = ["json"] }
+axum-server = { version = "0.7", features = ["tls-rustls"] }
+rcgen = "0.13"

web/frontend-server/src/main.rs

@@ -3,6 +3,8 @@
 //! 1. Reverse-proxies `/api/*` requests to the backend container.
 //! 2. Serves the built Vite SPA bundle from `dist/` (static files).
 //! 3. Falls back to `index.html` for any unmatched route (SPA history mode).
+//! 4. Serves over HTTPS with a self-signed cert (required for Web Crypto API
+//!    on non-localhost addresses; browsers disable crypto.subtle on plain HTTP).
 
 use axum::{
     body::Body,
@@ -13,6 +15,7 @@ use axum::{
     Router,
 };
 use std::env;
+use std::sync::Arc;
 use tower_http::services::{ServeDir, ServeFile};
 use tower_http::trace::TraceLayer;
 
@@ -30,8 +33,12 @@ async fn main() {
         .unwrap_or_else(|_| "8080".to_string())
         .parse()
         .expect("FRONTEND_PORT must be a number");
+    let use_tls = env::var("FRONTEND_TLS")
+        .map(|v| v == "1" || v.eq_ignore_ascii_case("true"))
+        .unwrap_or(true); // TLS on by default (Web Crypto requires HTTPS)
 
     let client = reqwest::Client::builder()
+        .danger_accept_invalid_certs(true) // backend is plain HTTP inside Docker
         .build()
         .expect("failed to build reqwest client");
 
@@ -40,25 +47,46 @@ async fn main() {
         client,
     };
 
-    // Static file serving with SPA fallback.
     let serve_dir = ServeDir::new("dist").fallback(ServeFile::new("dist/index.html"));
 
     let app = Router::new()
-        // Proxy /api and everything under /api/ to the backend.
         .route("/api", any(proxy_to_backend))
         .route("/api/*path", any(proxy_to_backend))
         .with_state(state)
-        // Everything else: static files + SPA fallback.
         .fallback_service(serve_dir)
         .layer(TraceLayer::new_for_http());
 
     let addr = format!("0.0.0.0:{port}");
-    eprintln!("Frontend server listening on {addr}");
-    eprintln!("Proxying /api/* to {backend_url}");
-    eprintln!("Serving static files from dist/");
 
-    let listener = tokio::net::TcpListener::bind(&addr).await.expect("bind failed");
-    axum::serve(listener, app).await.expect("server error");
+    if use_tls {
+        eprintln!("Generating self-signed TLS certificate...");
+        let cert = rcgen::generate_simple_self_signed(vec!["localhost", "normogen"])
+            .expect("failed to generate cert");
+        let cert_der = rcgen::Certificate::der(&cert);
+        let key_der = rcgen::Certificate::serialize_der_key(&cert);
+        let rustls_cert = axum_server::tls_rustls::RustlsConfig::from_der(
+            cert_der.to_vec(),
+            key_der.to_vec(),
+        )
+        .await
+        .expect("failed to build rustls config");
+
+        eprintln!("Frontend server listening on https://{addr} (TLS)");
+        eprintln!("Proxying /api/* to {backend_url}");
+        eprintln!("Serving static files from dist/");
+
+        axum_server::bind_rustls(addr.parse().expect("bad addr"), rustls_cert)
+            .serve(app.into_make_service())
+            .await
+            .expect("server error");
+    } else {
+        eprintln!("Frontend server listening on http://{addr} (no TLS)");
+        eprintln!("Proxying /api/* to {backend_url}");
+        eprintln!("Serving static files from dist/");
+
+        let listener = tokio::net::TcpListener::bind(&addr).await.expect("bind failed");
+        axum::serve(listener, app).await.expect("server error");
+    }
 }
 
 /// Forward a request to the backend, preserving method, headers, body, and