Billing upgrade/downgrade, inviti in app e diretta YouTube da mobile.

Upgrade Stripe con addebito immediato; downgrade programmato a fine periodo.
UX billing più sobria con box info; icone piani. API inviti e OAuth YouTube
per staff trasmissione; deep link join; scelta partita programmata o nuova.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/views/public/clubs/billing.html.erb

@@ -6,6 +6,9 @@
   <%= render "shared/club_subscription_status", club: @club, entitlements: @entitlements, subscription: @subscription, on_billing_page: true %>
 
   <%= render "shared/stripe_secure_payment" %>
+  <% if MatchLiveTv.stripe_enabled? %>
+    <%= render "shared/plan_change_info", subscription: @subscription %>
+  <% end %>
   <%= render "shared/plan_cards", show_stripe_portal: false %>
   <%= render "shared/subscription_cancel", club: @club, subscription: @subscription %>