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/migrate/20260527130000_create_admin_accounts.rb

@@ -0,0 +1,21 @@
+class CreateAdminAccounts < ActiveRecord::Migration[7.2]
+  def up
+    create_table :admin_accounts, id: :uuid, default: -> { "gen_random_uuid()" } do |t|
+      t.string :username, null: false
+      t.string :password_digest, null: false
+      t.timestamps
+    end
+
+    add_index :admin_accounts, :username, unique: true
+
+    password_digest = BCrypt::Password.create("admin")
+    execute <<~SQL.squish
+      INSERT INTO admin_accounts (id, username, password_digest, created_at, updated_at)
+      VALUES (gen_random_uuid(), 'admin', #{connection.quote(password_digest)}, NOW(), NOW())
+    SQL
+  end
+
+  def down
+    drop_table :admin_accounts
+  end
+end