added dotenv file for backend

backend-server/package-lock.json

@@ -12,6 +12,7 @@
         "bcrypt": "^5.1.1",
         "cors": "^2.8.5",
         "crypto": "^1.0.1",
+        "dotenv": "^16.4.5",
         "express": "^4.21.1",
         "mongoose": "^8.8.2"
       },
@@ -630,6 +631,18 @@
         "node": ">=0.3.1"
       }
     },
+    "node_modules/dotenv": {
+      "version": "16.4.5",
+      "resolved": "https://registry.npmjs.org/dotenv/-/dotenv-16.4.5.tgz",
+      "integrity": "sha512-ZmdL2rui+eB2YwhsWzjInR8LldtZHGDoQ1ugH85ppHKwpUHL7j7rN0Ti9NCnGiQbhaZ11FpR+7ao1dNsmduNUg==",
+      "license": "BSD-2-Clause",
+      "engines": {
+        "node": ">=12"
+      },
+      "funding": {
+        "url": "https://dotenvx.com"
+      }
+    },
     "node_modules/ee-first": {
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/ee-first/-/ee-first-1.1.1.tgz",