fix setup flow stale state and Stripe URL issues

Onboarding: re-fetch setup_status() after provider/Stripe connect instead
of manually patching the local assigns, which could miss admin_created and
leave users stuck on the setup page with no way forward.

Dev config: respect PHX_HOST for endpoint URL so Stripe checkout redirects
to the correct host instead of always using localhost.

Stripe setup: detect private/LAN IPs (10.x, 172.16-31.x, 192.168.x) as
unreachable, not just localhost — prevents creating webhook endpoints that
Stripe can never reach.

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

lib/berrypod/stripe/setup.ex

@@ -79,12 +79,25 @@ defmodule Berrypod.Stripe.Setup do
   end
 
   @doc """
-  Returns true if the app is running on localhost (Stripe can't reach it).
+  Returns true if the app URL is unreachable from Stripe's servers
+  (localhost, loopback, or private/LAN IPs).
   """
   def localhost? do
     url = BerrypodWeb.Endpoint.url()
     uri = URI.parse(url)
-    uri.host in ["localhost", "127.0.0.1", "0.0.0.0", "::1"]
+    unreachable_host?(uri.host)
+  end
+
+  defp unreachable_host?(host) when host in ["localhost", "0.0.0.0", "::1"], do: true
+
+  defp unreachable_host?(host) do
+    case :inet.parse_address(String.to_charlist(host)) do
+      {:ok, {127, _, _, _}} -> true
+      {:ok, {10, _, _, _}} -> true
+      {:ok, {172, b, _, _}} when b >= 16 and b <= 31 -> true
+      {:ok, {192, 168, _, _}} -> true
+      _ -> false
+    end
   end
 
   defp maybe_create_webhook(api_key) do