Refactor code structure for improved readability and maintainability

package-lock.json

@@ -9,6 +9,7 @@
             "version": "0.1.0",
             "dependencies": {
                 "bcryptjs": "^3.0.3",
+                "dotenv": "^17.2.3",
                 "express": "^4.19.2",
                 "jsonwebtoken": "^9.0.3",
                 "mysql2": "^3.16.2",
@@ -1354,6 +1355,17 @@
                 "npm": "1.2.8000 || >= 1.4.16"
             }
         },
+        "node_modules/dotenv": {
+            "version": "17.2.3",
+            "resolved": "https://registry.npmjs.org/dotenv/-/dotenv-17.2.3.tgz",
+            "integrity": "sha512-JVUnt+DUIzu87TABbhPmNfVdBDt18BLOWjMUFJMSi/Qqg7NTYtabbvSNJGOJ7afbRuv9D/lngizHtP7QyLQ+9w==",
+            "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",