Reduce heartbeat interval from 120 seconds to 90 seconds for improved responsiveness

lib/services/supabase_heartbeat.dart

@@ -81,8 +81,8 @@ void initHeartbeat() {
         print("Error sending heartbeat: $e");
       }
 
-      // Wait 120 seconds (2 minutes) before sending the next heartbeat
+      // Wait 90 seconds (1.5 minutes) before sending the next heartbeat
-      await Future.delayed(Duration(seconds: 120));
+      await Future.delayed(Duration(seconds: 90));
     }
 
   }, null);