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/admin/providers/index.ex

@@ -3,6 +3,7 @@ defmodule BerrypodWeb.Admin.Providers.Index do
 
   alias Berrypod.Products
   alias Berrypod.Products.ProviderConnection
+  alias Berrypod.Providers.Provider
 
   @impl true
   def mount(_params, _session, socket) do
@@ -11,6 +12,7 @@ defmodule BerrypodWeb.Admin.Providers.Index do
     {:ok,
      socket
      |> assign(:page_title, "Provider connections")
+     |> assign(:available_providers, Provider.available())
      |> stream(:connections, connections)}
   end
 
@@ -85,6 +87,13 @@ defmodule BerrypodWeb.Admin.Providers.Index do
     """
   end
 
+  defp provider_name(type) do
+    case Provider.get(type) do
+      %{name: name} -> name
+      nil -> String.capitalize(type)
+    end
+  end
+
   defp format_relative_time(datetime) do
     diff = DateTime.diff(DateTime.utc_now(), datetime, :second)