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/config/initializers/sidekiq.rb

@@ -5,6 +5,7 @@ Sidekiq.configure_server do |config|
 
   config.on(:startup) do
     StreamPublisherSyncJob.ensure_chain
+    Ops::HealthMonitorJob.ensure_chain
   end
 end