test(auth,admin,companies,creators,settings): add 325 comprehensive test methods

Covers Auth (registration, login, email verification, password reset, username validation),
Admin (user management, company approval, impersonation, audit log, dashboard stats),
Companies (profile CRUD, social link normalization, completion scoring, approval flow),
Creators (profile CRUD, username throttle, completion scoring, scopes, policies),
and Settings (platform settings CRUD, caching, CSS generation, feature flags).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>