Aggiunge l'autoscaler streaming con warm spare e kill-switch.

Scala i nodi overflow quando gli slot calano, mantiene una spare a caldo sotto carico e spegne gli idle, disattivabile con STREAM_AUTOSCALE_ENABLED.

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

backend/app/jobs/streams/autoscaler_job.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module Streams
+  class AutoscalerJob
+    include Sidekiq::Job
+
+    sidekiq_options retry: 1, queue: "default"
+
+    INTERVAL_SECS = ENV.fetch("STREAM_AUTOSCALE_INTERVAL_SECS", "60").to_i
+    REDIS_CHAIN_KEY = "streams:autoscaler:chain"
+
+    def self.ensure_chain
+      return unless redis
+      return if redis.get(REDIS_CHAIN_KEY)
+
+      redis.set(REDIS_CHAIN_KEY, "1", ex: INTERVAL_SECS * 2)
+      perform_in(INTERVAL_SECS)
+    end
+
+    def self.redis
+      @redis ||= Redis.new(url: ENV.fetch("REDIS_URL", "redis://localhost:6379/0"))
+    rescue Redis::CannotConnectError
+      nil
+    end
+
+    def perform
+      Streams::Autoscaler.reconcile!
+    ensure
+      self.class.redis&.set(REDIS_CHAIN_KEY, "1", ex: INTERVAL_SECS * 2)
+      self.class.perform_in(INTERVAL_SECS)
+    end
+  end
+end