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/teams/billing.html.erb

@@ -8,7 +8,7 @@
   <div class="plans">
     <% @plans.each do |plan| %>
       <div class="plan-card">
-        <h3><%= plan.name %></h3>
+        <%= render "shared/plan_title", plan: plan %>
         <% if plan.slug == "free" %>
           <div class="plan-price">€0</div>
         <% elsif plan.slug == "premium_light" %>
@@ -27,7 +27,6 @@
         <% if plan.slug == @entitlements.plan.slug %>
           <span class="btn btn-secondary" style="opacity:0.7">Piano attuale</span>
         <% elsif plan.slug == "free" %>
-          <p style="color:#888;font-size:0.85rem">Contatta il supporto per downgrade.</p>
         <% elsif MatchLiveTv.stripe_enabled? %>
           <%= link_to "Gestisci abbonamento società", public_club_billing_path(@team.club), class: "btn btn-primary" %>
         <% else %>