test: centralize demo IDs and site_domain mock in env.ts

- Added testing_site_id, testing_site_domain_id, testing_fqdn, testing_person_id
- Created mock_site_domain object matching +layout.ts expectations
- Updated minimal_v3_mocks.ts to use mock_site_domain
- Fixes 'Domain Not Registered' overlay in Playwright tests
- All test IDs now documented with comments from tests/README.md

tests/_helpers/minimal_v3_mocks.ts

@@ -1,4 +1,5 @@
 import { Page } from '@playwright/test';
+import { mock_site_domain } from './env';
 
 export const minimal_event = (event_id: string) => ({
   data: {
@@ -36,7 +37,11 @@ export async function attach_minimal_v3_routes(page: Page, event_id: string) {
     const method = req.method();
 
     if (url.includes('site_domain/search')) {
-      return route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify({ data: [{ id: 'td', site_id: 'ts' }] }) });
+      return route.fulfill({
+        status: 200,
+        contentType: 'application/json',
+        body: JSON.stringify({ data: [mock_site_domain] })
+      });
     }
 
     if (url.includes(`/v3/crud/event/${event_id}`) && method === 'GET') {