extract setup wizard to dedicated /admin/setup page

Move the setup stepper out of the dashboard into its own LiveView.
Dashboard now redirects to setup when site isn't live, and shows
stats-only view once live. Also cleans up button component variant
handling, fixes alert CSS, and removes stale demo.html.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/berrypod_web/components/core_components.ex

@@ -81,16 +81,24 @@ defmodule BerrypodWeb.CoreComponents do
   """
   attr :rest, :global, include: ~w(href navigate patch method download name value disabled)
   attr :class, :string
-  attr :variant, :string, values: ~w(primary)
+  attr :variant, :string, values: ~w(primary outline)
   slot :inner_block, required: true
 
   def button(%{rest: rest} = assigns) do
-    variants = %{"primary" => "admin-btn-primary", nil => "admin-btn-primary admin-btn-soft"}
+    variants = %{
+      "primary" => "admin-btn-primary",
+      "outline" => "admin-btn-outline",
+      nil => "admin-btn-primary admin-btn-soft"
+    }
+
+    variant_class = Map.fetch!(variants, assigns[:variant])
 
     assigns =
-      assign_new(assigns, :class, fn ->
-        ["admin-btn", Map.fetch!(variants, assigns[:variant])]
-      end)
+      assign(assigns, :class, [
+        "admin-btn",
+        variant_class,
+        assigns[:class]
+      ])
 
     if rest[:href] || rest[:navigate] || rest[:patch] do
       ~H"""