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/admin/layout_test.exs

@@ -30,13 +30,6 @@ defmodule BerrypodWeb.Admin.LayoutTest do
       refute has_element?(view, ~s(a.active[href="/admin/settings"]))
     end
 
-    test "highlights setup on setup page", %{conn: conn} do
-      {:ok, view, _html} = live(conn, ~p"/admin/setup")
-
-      assert has_element?(view, ~s(a.active[href="/admin/setup"]))
-      refute has_element?(view, ~s(a.active[href="/admin/orders"]))
-    end
-
     test "highlights correct link on different pages", %{conn: conn} do
       {:ok, view, _html} = live(conn, ~p"/admin/settings")