bugfix: .env.example files updated. some minor changes in jwt strategy to avoid failing when .env files does not contain needed keys.

backend/.env.example

@@ -1,23 +1,41 @@
 # Database
-DATABASE_URL=postgresql://dyolink_user:password@postgres:5432/dyolink_db
-POSTGRES_HOST=postgres
+#
+# Local dev (Nest on your machine + Postgres via docker-compose.postgres.yml):
+#   Use host "localhost" — hostname "postgres" only works inside Docker networks.
+DATABASE_URL=postgresql://dyolink_user:password@localhost:5432/dyolink_db
+POSTGRES_HOST=localhost
 POSTGRES_PORT=5432
 POSTGRES_USER=dyolink_user
-POSTGRES_PASSWORD=CHANGE_ME_IN_PRODUCTION
+POSTGRES_PASSWORD=password
 POSTGRES_DB=dyolink_db
+#
+# If you run the API inside the same Compose stack as Postgres, use instead:
+# DATABASE_URL=postgresql://dyolink_user:password@postgres:5432/dyolink_db
+# POSTGRES_HOST=postgres
 
-# JWT
+# JWT (required for register/login)
 JWT_SECRET=CHANGE_ME_TO_A_STRONG_SECRET_32_CHARS_MIN
 JWT_EXPIRES_IN=7d
+JWT_REFRESH_SECRET=CHANGE_ME_TO_ANOTHER_STRONG_SECRET
+JWT_REFRESH_EXPIRES_IN=30d
 
 # Application
 PORT=3000
 NODE_ENV=development
 API_PREFIX=/api
-CORS_ORIGIN=http://localhost:3000
+# CORS and invite links — must match the URL where the Next.js app runs
+FRONTEND_URL=http://localhost:3001
+
+# OAuth (optional — uncomment when configured)
+# GOOGLE_CLIENT_ID=your-google-client-id
+# GOOGLE_CLIENT_SECRET=your-google-client-secret
+# GOOGLE_CALLBACK_URL=http://localhost:3000/auth/google/callback
+# FACEBOOK_CLIENT_ID=your-facebook-app-id
+# FACEBOOK_CLIENT_SECRET=your-facebook-app-secret
+# FACEBOOK_CALLBACK_URL=http://localhost:3000/auth/facebook/callback
 
 # Email (configure for production)
 SMTP_HOST=smtp.gmail.com
 SMTP_PORT=587
 SMTP_USER=your_email@gmail.com
-SMTP_PASSWORD=your_app_password
+SMTP_PASSWORD=your_app_password