Admin protetto, dashboard KPI e aggiornamenti sito marketing.

Login admin con cambio password, metriche server (CPU/RAM/disco/banda), grafici e statistiche streaming; sezione piani ridimensionata.

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

backend/app/views/admin/teams/index.html.erb

@@ -1,5 +1,5 @@
 <h2>Teams</h2>
-<table>
+<table class="admin-table">
   <thead><tr><th>Nome</th><th>Sport</th><th>YouTube</th></tr></thead>
   <tbody>
     <% @teams.each do |t| %>