added test coverage for app.java and fixed random to be thread safe #2973

Author: skamble2

rate-limiting-pattern/src/main/java/com/iluwatar/rate/limiting/pattern/App.java

@@ -106,6 +106,7 @@ static Runnable createClientTask(
       String[] operations = {
         "GetObject", "PutObject", "Query", "Scan", "PutItem", "Invoke", "ListFunctions"
       };
+      // Safe: ThreadLocalRandom is used per-thread for concurrent simulation
       ThreadLocalRandom random = ThreadLocalRandom.current();
 
       while (running.get() && !Thread.currentThread().isInterrupted()) {