fix(rustproxy): Use cooperative cancellation for background tasks, prune stale caches and metric entries, and switch tests to dynamic port allocation to avoid port conflicts

rust/crates/rustproxy-http/src/proxy_service.rs

@@ -167,6 +167,14 @@ impl HttpProxyService {
         self.backend_tls_config = config;
     }
 
+    /// Prune caches for route IDs that are no longer active.
+    /// Call after route updates to prevent unbounded growth.
+    pub fn prune_stale_routes(&self, active_route_ids: &std::collections::HashSet<String>) {
+        self.route_rate_limiters.retain(|k, _| active_route_ids.contains(k));
+        self.regex_cache.clear();
+        self.upstream_selector.reset_round_robin();
+    }
+
     /// Handle an incoming HTTP connection on a plain TCP stream.
     pub async fn handle_connection(
         self: Arc<Self>,