add setup onboarding page, dashboard launch checklist, provider registry

- new /setup page with three-section onboarding (account, provider, payments)
- dashboard launch checklist with progress bar, go-live, dismiss
- provider registry on Provider module (single source of truth for metadata)
- payments registry for Stripe
- setup context made provider-agnostic (provider_connected, theme_customised, etc.)
- admin provider pages now fully registry-driven (no hardcoded provider names)
- auth flow: fresh installs redirect to /setup, signed_in_path respects setup state
- removed old /admin/setup wizard
- 840 tests, 0 failures

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/berrypod_web/live/auth/registration.ex

@@ -54,8 +54,8 @@ defmodule BerrypodWeb.Auth.Registration do
        |> put_flash(:error, "Registration is closed")
        |> redirect(to: ~p"/users/log-in")}
     else
-      changeset = Accounts.change_user_email(%User{}, %{}, validate_unique: false)
-      {:ok, assign_form(socket, changeset), temporary_assigns: [form: nil]}
+      # Fresh install — account creation happens on the setup page
+      {:ok, redirect(socket, to: ~p"/setup")}
     end
   end