refactor: change backend to typescript and update types and variables accordingly

backend/package.json

@@ -2,22 +2,27 @@
   "name": "backend",
   "version": "0.0.0-dev",
   "description": "",
-  "main": "server.js",
+  "main": "server.ts",
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
-    "start": "node server.js",
-    "dev": "node --watch server.js"
+    "start": "node server.ts",
+    "dev": "node --watch server.ts"
   },
   "keywords": [],
   "author": "",
   "license": "ISC",
   "type": "module",
   "dependencies": {
+    "@stockhome/shared": "1.0.0",
     "cors": "^2.8.5",
     "dotenv": "^17.2.3",
     "ejs": "^3.1.10",
     "express": "^5.2.1",
     "jose": "^6.0.12",
     "mysql2": "^3.16.0"
+  },
+  "devDependencies": {
+    "@types/express": "^5.0.6",
+    "@types/node": "^26.1.0"
   }
-}
+}