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/user_auth.ex

@@ -258,7 +258,7 @@ defmodule BerrypodWeb.UserAuth do
 
   @doc "Returns the path to redirect to after log in."
   def signed_in_path(_) do
-    if Berrypod.Settings.site_live?(), do: ~p"/admin", else: ~p"/admin/setup"
+    if Berrypod.Setup.setup_status().setup_complete, do: ~p"/admin", else: ~p"/setup"
   end
 
   @doc """