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>

test/berrypod_web/live/auth/confirmation_test.exs

@@ -64,7 +64,7 @@ defmodule BerrypodWeb.Auth.ConfirmationTest do
       assert Accounts.get_user!(user.id).confirmed_at
       # we are logged in now
       assert get_session(conn, :user_token)
-      assert redirected_to(conn) == ~p"/admin/setup"
+      assert redirected_to(conn) == ~p"/setup"
 
       # log out, new conn
       conn = build_conn()