feat: add environment configuration and required variables

src/config/env.ts

@@ -0,0 +1,25 @@
+import dotenv from "dotenv";
+
+dotenv.config();
+
+function requireEnv(key: string): string {
+  const value = process.env[key];
+
+  if (!value) {
+    throw new Error(`Environment variable ${key} is required but not set.`);
+  }
+
+  return value;
+}
+
+export const env = {
+  nodeEnv: process.env.NODE_ENV ?? "development",
+  port: Number(process.env.PORT) ?? 3000,
+
+  mongoUri: requireEnv("MONGO_URI"),
+
+  jwtSecret: {
+    secret: requireEnv("JWT_SECRET"),
+    expiresIn: process.env.JWT_EXPIRES_IN ?? "1h",
+  },
+};