Cache and restore authenticated session state across Cypress tests using cy.session()

Steps

1. Call `cy.session(id, setup)` with a string/array/object `id` and a required `setup` function that performs the login flow once
2. Rely on Cypress caching cookies, `localStorage`, and `sessionStorage` (across all domains) under that `id` and restoring them instantly on subsequent calls with the same `id`
3. Pass an `options.validate` callback to re-verify the restored session is still good; a failing assertion, thrown exception, or rejected promise invalidates the cache and re-runs `setup`
4. Set `options.cacheAcrossSpecs: true` to share the in-memory session across every spec file in the same Cypress run (not written to disk, not shared across machines/runs)
5. Keep the `id`, `setup`, `validate`, and `cacheAcrossSpecs` identical everywhere the same session is reused — Cypress throws if two calls with the same `id` disagree on any of them
6. Call `cy.session()` at the start of each test rather than only in a global `before` hook, since sessions are restored per test, not persisted automatically between tests