Implement create organization onboarding page in console/account

[wauputr4]

Goal

Implement the dedicated frontend flow for creating/onboarding a new organization when it is not available to claim yet.

Scope

• Add the chosen route/page for organization onboarding/create flow.
• Add clear entry points from account/console/search empty states based on the UX spec.
• Build the form using existing design system and i18n patterns.
• Reuse the existing organization create capability where appropriate, without exposing superadmin-only affordances to normal users.
• Handle loading, validation, success, duplicate slug/name, unauthenticated, unauthorized, and empty/error states.

Acceptance criteria

• A user can find a clear "create organization" path when their organization is not listed.
• The form is usable on mobile and desktop in light/dark mode.
• Success state tells the user what happens next and where to manage/track the organization.
• Frontend checks/build pass, or skipped checks are documented.

Depends on

• UX/spec issue: Define organization creation onboarding UX and entry points #78