Aggiunge monitoraggio ops: health check, log scanner, dashboard e notifiche.

Introduce incidenti con dedup, job Sidekiq ogni 3 min, scan log cron, /up/deep,
dashboard /admin/ops e push ntfy; include Sentry opzionale e fix test suite.

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

backend/app/views/ops/alert_mailer/incident.text.erb

@@ -0,0 +1,10 @@
+<%= @incident.title %>
+
+Severità: <%= @incident.severity %>
+Tipo: <%= @incident.kind %>
+Occorrenze: <%= @incident.occurrence_count %>
+Ultimo avvistamento: <%= @incident.last_seen_at %>
+
+<%= @incident.message %>
+
+Dashboard: <%= ENV.fetch("APP_PUBLIC_URL", "https://www.matchlivetv.it").chomp("/") %>/admin/ops