add Site context with social links editor and site-wide settings

- Add Site context for managing site-wide content (social links, nav items,
  announcement bar, footer content)
- Add SocialLink schema with URL normalization and platform auto-detection
  supporting 40+ platforms via host and 25+ via URI scheme
- Add NavItem schema for header/footer navigation (editor UI coming next)
- Add SiteEditor component with collapsible sections for each content type
- Wire social links card block and footer to use database data
- Filter empty URLs from display in shop components
- Add DetailsPreserver hook to preserve collapsible section state
- Add comprehensive tests for Site context and SocialLink functions
- Remove unused helper functions from onboarding to fix compiler warnings
- Move sync_edit_url_param helper to group handle_editor_event clauses

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/berrypod_web/live/setup/onboarding.ex

@@ -851,36 +851,6 @@ defmodule BerrypodWeb.Setup.Onboarding do
 
   # ── Helpers ──
 
-  defp account_summary(%{current_scope: %{user: user}}) when not is_nil(user) do
-    site_name = Settings.site_name()
-
-    if site_name != "Store Name" do
-      "#{site_name} · #{user.email}"
-    else
-      user.email
-    end
-  end
-
-  defp account_summary(_), do: "Account created"
-
-  defp provider_summary(%{setup: %{provider_type: type}}) when is_binary(type) do
-    case Provider.get(type) do
-      nil -> "Connected"
-      info -> "Connected to #{info.name}"
-    end
-  end
-
-  defp provider_summary(_), do: nil
-
-  defp stripe_summary(%{setup: %{stripe_connected: true}}) do
-    case Settings.secret_hint("stripe_api_key") do
-      nil -> "Connected"
-      hint -> "Connected · #{hint}"
-    end
-  end
-
-  defp stripe_summary(_), do: nil
-
   defp provider_card_options(providers) do
     Enum.map(providers, fn provider ->
       option = %{