How do you implement database transactions in Node.js using Sequelize to ensure multiple related writes succeed or fail together?

Sequelize's transaction() method wraps multiple operations so that either all of them commit together or, if any operation throws, all of them are automatically rolled back -- essential for maintaining data consistency in multi-step operations like transferring funds between two accounts, where partially applying only one side of the transfer would leave the data in an invalid, inconsistent state.

const transaction = await sequelize.transaction();
try {
  await Account.decrement('balance', { by: 100, where: { id: fromId }, transaction });
  await Account.increment('balance', { by: 100, where: { id: toId }, transaction });
  await transaction.commit();
} catch (err) {
  await transaction.rollback();
  throw err;
}