Webberdoo Starter 2.0 controller structure

All application HTTP controllers now live under src/Controllers/.

Layout:
  src/Controllers/Account/       Browser account/auth-related account pages
  src/Controllers/Admin/         Admin UI and admin data endpoints
  src/Controllers/Api/V1/        Versioned mobile/public API endpoints
  src/Controllers/Billing/       Browser billing and Stripe webhook endpoints
  src/Controllers/Platform/      Home and health endpoints
  src/Controllers/Security/      Login/logout/email verification
  src/Controllers/Settings/      Admin settings endpoints
  src/Controllers/User/          User React application shell

Domain code remains in its existing modules (Billing, Entitlement, Settings,
Sync, Account, etc.). Only the HTTP/controller layer has been centralized.

The old controller file paths are included as harmless PHP stubs in this patch
so this changed-files-only ZIP can safely overwrite an existing copy without
leaving duplicate attributed routes behind. Those stub files may be deleted
later if desired.

No .env file is included or changed.