Add user GET endpoint, schemas, and security middlewares

Introduces GET /users/:id endpoint with validation schema, adds tests for user and register routes, and applies security middlewares (helmet, hpp, cors) to the server. Also adds ESLint configuration and updates logger with linting comments.

schemas/users/[id].js

@@ -0,0 +1,15 @@
+const z = require("zod")
+
+module.exports = {
+    GET: {
+        headers: z.object({
+            authorization: z.string()
+            .startsWith("Bearer ", { message: "Token d'authentification manquant ou invalide." }),
+            "content-type": z.string().regex(/application\/json/i).optional()
+        }),
+        error: {
+            code: 422,
+            message: "Invalid request data"
+        }
+    }
+}