Add initial setup wizard for first-time deployment

[hbbayrak]

Summary

When no organizations exist, the settings page displays an initial setup wizard that allows superadmin to configure:

• Deployment settings (name, country, admin levels, metabase URL, funding sources)
• First organization with service toggles
• First admin user with permissions

Changes

Server

• InitialSetupRequest.cs: New request model with validation attributes
• SettingsController.cs: New POST /initial-setup endpoint with atomic transaction

Client

• SettingsPage.tsx: Refactored to show setup wizard when no orgs exist
• DeploymentSettingsFields.tsx: Shared component for deployment settings (reduces duplication)
• validations.ts: Added InitialSetupFormSchema with required field validation
• organizations/api.ts: Added useHasOrganizations() hook for setup detection

Features

• Server-side validation with Data Annotations
• Client-side validation with Zod schemas
• Atomic transaction ensuring all-or-nothing setup
• Shared component for code reuse between setup and normal settings modes

Test Plan

• Fresh database: Login as superadmin, verify setup wizard appears
• Fill all required fields, submit - verify org and user created
• Logout, login with new admin account - verify full app access
• Refresh settings page - verify setup wizard no longer appears
• Try setup endpoint again - verify it fails (already initialized)