Add dotenv support and bulk SMS endpoint

- Integrated dotenv for environment variable management.
- Updated queueWorker to use WORKER_INTERVAL from .env or default to 5 seconds.
- Added a new bulk SMS endpoint to queue multiple messages in a single request, with validation and transaction handling.
- Updated package.json and package-lock.json to include dotenv dependency.

queueWorker.js

@@ -45,7 +45,7 @@ function startQueueWorker(io) {
                 });
             }
         });
-    }, 5000); // Check every 5 seconds
+    }, parseInt(process.env.WORKER_INTERVAL) || 5000); // Check based on interval from .env or default to 5 seconds
 }
 
 module.exports = startQueueWorker;