fix(rustproxy-http): improve HTTP/3 connection reuse and clean up stale proxy state

rust/crates/rustproxy/src/lib.rs

@@ -363,6 +363,7 @@ impl RustProxy {
         // Start the throughput sampling task with cooperative cancellation
         let metrics = Arc::clone(&self.metrics);
         let conn_tracker = self.listener_manager.as_ref().unwrap().conn_tracker().clone();
+        let http_proxy = self.listener_manager.as_ref().unwrap().http_proxy().clone();
         let interval_ms = self.options.metrics.as_ref()
             .and_then(|m| m.sample_interval_ms)
             .unwrap_or(1000);
@@ -378,6 +379,9 @@ impl RustProxy {
                         metrics.sample_all();
                         // Periodically clean up stale rate-limit timestamp entries
                         conn_tracker.cleanup_stale_timestamps();
+                        // Clean up expired rate limiter entries to prevent unbounded
+                        // growth from unique IPs after traffic stops
+                        http_proxy.cleanup_all_rate_limiters();
                     }
                 }
             }