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/login.ex

@@ -12,14 +12,17 @@ defmodule BerrypodWeb.Auth.Login do
           <.header>
             <p>Log in</p>
             <:subtitle>
-              <%= if @current_scope do %>
-                You need to reauthenticate to perform sensitive actions on your account.
-              <% else %>
-                Don't have an account? <.link
-                  navigate={~p"/users/register"}
-                  class="font-semibold text-brand hover:underline"
-                  phx-no-format
-                >Sign up</.link> for an account now.
+              <%= cond do %>
+                <% @current_scope -> %>
+                  You need to reauthenticate to perform sensitive actions on your account.
+                <% @registration_open -> %>
+                  Don't have an account? <.link
+                    navigate={~p"/setup"}
+                    class="font-semibold text-brand hover:underline"
+                    phx-no-format
+                  >Set up your shop</.link> to get started.
+                <% true -> %>
+                  Log in with your admin credentials.
               <% end %>
             </:subtitle>
           </.header>
@@ -100,7 +103,8 @@ defmodule BerrypodWeb.Auth.Login do
 
     form = to_form(%{"email" => email}, as: "user")
 
-    {:ok, assign(socket, form: form, trigger_submit: false)}
+    {:ok,
+     assign(socket, form: form, trigger_submit: false, registration_open: !Accounts.has_admin?())}
   end
 
   @impl true

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