Fix Mini fork leftovers in POS config

After an auto-logout, silent re-auth fails with login_required and
SsoLoginController@callback redirects to config('ladill.marketing_url') — which
still defaulted to https://ladill.com/products/mini, dumping POS users on Mini's
product page. Point ladill.product_slug/marketing_url at POS.

Also fix the identity service key (config/identity.php + services.ladill_identity
read IDENTITY_API_KEY_MINI; POS provisions IDENTITY_API_KEY_POS) and tidy the
remaining Mini defaults (app.name, ladill_sso redirect, mobile-topbar app_name).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

config/ladill.php

@@ -1,6 +1,6 @@
 <?php
 
 return [
-    'product_slug' => 'mini',
-    'marketing_url' => env('LADILL_MARKETING_URL', 'https://ladill.com/products/mini'),
+    'product_slug' => 'pos',
+    'marketing_url' => env('LADILL_MARKETING_URL', 'https://ladill.com/products/pos'),
 ];