Switches `vitest.config.js` to `environmentMatchGlobs` so source-reading specs keep Node URL resolution while Vue specs run under jsdom. Adds an in-memory `localStorage`/`sessionStorage` polyfill (and ResizeObserver/IntersectionObserver fallbacks) to `tests/unit/setup.js` so jsdom 29 + vitest 4 environments that ship no localStorage stop crashing the 109 unit tests that touched SessionUser / InvoicingBillingPeriod caches at module-load time.
Test result: 1343/1343 fast + 1688/1688 serial pass (was 1195/1304 on master). All 197 invoicing-period / invoice-distribution / superuser-invoices / xlvask-usage-amount-cache tests green.
- Introduced `.prettierrc.json` to enforce consistent code formatting across the project.
- Updated unit and e2e test files to address formatting issues, improve readability, and ensure alignment with the new Prettier configuration.
- Delete outdated tests for `useSelfServeLogic` composable, step navigation, and validation related to the Self-Serve module.
- These tests have been deprecated in favor of newer, streamlined testing strategies and refactored logic.
Jeppe B