docs: Update .env.example with new JWT refresh settings

backend/.env.example

@@ -8,11 +8,13 @@ DATA_STATE=new_jersey
 LOG_LEVEL=INFO
 DEV_MODE=true
 FRONTEND_URL=http://localhost:5173
+API_V1_STR=/api/v1
 
 # Security & JWT Configuration
 SECRET_KEY=change-me-in-production
 ALGORITHM=HS256
 ACCESS_TOKEN_EXPIRE_MINUTES=30
+REFRESH_TOKEN_EXPIRE_DAYS=7
 
 # Voter Database Configuration
 DB_HOST=localhost