refactor: allow disabling heartbeat timer to meet testcase requirements

src/aura_engine/plugins/monitor.py

@@ -309,10 +309,9 @@ class AuraMonitor:
                     {"engine_id": self.engine_id, "status": status}
                 )
 
-        heartbeat_frq = self.config.monitoring.heartbeat.frequency  # default: 1
-        if int(heartbeat_frq or 0) < 1:
-            heartbeat_frq = 1
-        threading.Timer(heartbeat_frq, self.heartbeat).start()
+        heartbeat_frq = self.config.monitoring.heartbeat.frequency  # default: 1, disable: 0
+        if heartbeat_frq > 1:
+            threading.Timer(heartbeat_frq, self.heartbeat).start()
 
     def validate_url_connection(self, url):
         """