feat: handle SIGTERM for graceful container stops (0.35.0)

`docker compose stop` and Kubernetes / Podman / systemd all send
SIGTERM first; SIGINT is for interactive shells. Without a SIGTERM
listener the container's stop-grace period elapses with the API still
running, then SIGKILL skips the daemon shutdown path and leaks
Chromium until the OS reaps the parent. Replace the bare
`tokio::signal::ctrl_c()` with a select over ctrl_c and
SignalKind::terminate() so the daemon.shutdown().await path runs in
both cases.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.34.0",
+  "version": "0.35.0",
   "private": true,
   "type": "module",
   "scripts": {