Retrieves the signup verification link for a Playwright test account. This allows E2E tests to complete the full signup flow by retrieving the verification link that would normally be sent via email. GET /account/test/playwright/signup-verification-link?email=...&appDomain=...&originUrl=... Headers: x-playwright-api-key: <your-api-key> Security: - Email MUST match iman+playwright-test-*@nebulr.group pattern - In PROD, requires PLAYWRIGHT_TESTDATA_ENABLED_PROD=true Returns: { link: string, token: string }