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/db/seeds.rb

@@ -1,5 +1,9 @@
 load Rails.root.join("db/seeds/plans.rb")
 
+AdminAccount.find_or_create_by!(username: "admin") do |a|
+  a.password = "admin"
+end
+
 coach = User.find_or_create_by!(email: "coach@matchlivetv.test") do |u|
   u.name = "Coach Demo"
   u.password = "password123"