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.

package-lock.json

@@ -9,6 +9,7 @@
       "version": "1.0.0",
       "license": "ISC",
       "dependencies": {
+        "dotenv": "^17.4.2",
         "express": "^4.18.2",
         "socket.io": "^4.7.4",
         "sqlite3": "^6.0.1"
@@ -328,6 +329,18 @@
         "node": ">=8"
       }
     },
+    "node_modules/dotenv": {
+      "version": "17.4.2",
+      "resolved": "https://registry.npmjs.org/dotenv/-/dotenv-17.4.2.tgz",
+      "integrity": "sha512-nI4U3TottKAcAD9LLud4Cb7b2QztQMUEfHbvhTH09bqXTxnSie8WnjPALV/WMCrJZ6UV/qHJ6L03OqO3LcdYZw==",
+      "license": "BSD-2-Clause",
+      "engines": {
+        "node": ">=12"
+      },
+      "funding": {
+        "url": "https://dotenvx.com"
+      }
+    },
     "node_modules/dunder-proto": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/dunder-proto/-/dunder-proto-1.0.1.tgz",