Hot-reload content on a NATS trigger instead of requiring a restart

questions is now Arc<ArcSwap<HashMap<...>>> - readers do a lock-free
atomic load (state.questions.load().get(&id).cloned()), never blocking
on or blocked by a reload. content::watch_for_reload subscribes to
portal.content.reload (published by the questions repo's own CI after
it lints a push - see that repo's lint-and-reload.yml) and swaps in a
freshly re-fetched HashMap on each message. A fetch/parse failure logs
and keeps serving the last-good content rather than clearing it.

Cargo.lock

@@ -2751,6 +2751,7 @@ name = "portal"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "arc-swap",
  "async-nats",
  "aws-sdk-s3",
  "axum",