chore(domains): add solbo.accounted.se to the production host inventory (#2378)

Solbo was provisioned on prod on 2026-09-01 (team ce8993e5, brand
6e3c78af) but never added to CUSTOMER_PRODUCTION_WHITE_LABEL_HOSTS. The
namespace rule already protects the host; the set is the checked-in
inventory the tests pin host by host, and it was stale.


Claude-Session: https://claude.ai/code/session_01NUNB7qjua8EUaJmZgfFscx

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

lib/domains/__tests__/production-white-label-backend.test.ts

@@ -17,6 +17,7 @@ const APPROVED_PRODUCTION_HOSTS = [
   'improveone.accounted.se',
   'm360.accounted.se',
   'redovisningskompaniet.accounted.se',
+  'solbo.accounted.se',
   'willem.accounted.se',
   'ziffr.accounted.se',
 ]

lib/domains/production-white-label-backend.ts

@@ -39,6 +39,7 @@ const CUSTOMER_PRODUCTION_WHITE_LABEL_HOSTS = new Set([
   'improveone.accounted.se',
   'm360.accounted.se',
   'redovisningskompaniet.accounted.se',
+  'solbo.accounted.se',
   'willem.accounted.se',
   'ziffr.accounted.se',
 ])