feat: distributed scheduling for version check job (#13042)

This change spreads Chatwoot Hub version checks across the day by
scheduling each installation at a stable minute derived from its
installation identifier, instead of having all instances check at the
same fixed time.

Closes
-
https://linear.app/chatwoot/issue/CW-6107/handle-the-spike-at-12-utc-on-chatwoot-hub

What changed
- Added `Internal::TriggerDailyScheduledItemsJob` to act as the daily
trigger for deferred internal jobs.
- Updated the version check cron entry to run once daily at `00:00 UTC`
and enqueue the actual version check for that installation’s assigned
minute of the day.
- Used a deterministic minute-of-day derived from
`ChatwootHub.installation_identifier` so the check time stays stable
across deploys and restarts.
- Kept the existing cron schedule key while switching it to the new
orchestrator job.

How to test
- Run `bundle exec rspec
spec/jobs/internal/check_new_versions_job_spec.rb
spec/jobs/internal/trigger_daily_scheduled_items_job_spec.rb
spec/configs/schedule_spec.rb`
- In a Rails console, run
`Internal::TriggerDailyScheduledItemsJob.perform_now` and verify
`Internal::CheckNewVersionsJob` is enqueued with a `wait_until` later
the same UTC day.
- In Super Admin settings, use Refresh and verify the version check
still runs immediately.

---------

Co-authored-by: Sojan Jose <sojan@pepalo.com>

spec/jobs/internal/trigger_daily_scheduled_items_job_spec.rb

@@ -0,0 +1,39 @@
+require 'rails_helper'
+
+RSpec.describe Internal::TriggerDailyScheduledItemsJob do
+  subject(:perform_job) { described_class.perform_now }
+
+  let(:installation_id) { 'test-installation-id' }
+  let(:designated_minute) { Digest::MD5.hexdigest(installation_id).hex % 1440 }
+  let(:scheduled_time) { Time.current.utc.beginning_of_day + designated_minute.minutes }
+  let(:configured_job) { instance_double(ActiveJob::ConfiguredJob, perform_later: true) }
+
+  before do
+    allow(ChatwootHub).to receive(:installation_identifier).and_return(installation_id)
+    allow(Internal::CheckNewVersionsJob).to receive(:set).and_return(configured_job)
+  end
+
+  it 'enqueues the job' do
+    expect { described_class.perform_later }.to have_enqueued_job(described_class)
+      .on_queue('scheduled_jobs')
+  end
+
+  it 'schedules the version check at a stable minute in production' do
+    allow(Rails.env).to receive(:production?).and_return(true)
+
+    travel_to Time.zone.parse('2026-03-17 08:00:00 UTC') do
+      perform_job
+
+      expect(Internal::CheckNewVersionsJob).to have_received(:set).with(wait_until: scheduled_time)
+      expect(configured_job).to have_received(:perform_later)
+    end
+  end
+
+  it 'does not schedule the version check outside production' do
+    allow(Rails.env).to receive(:production?).and_return(false)
+
+    perform_job
+
+    expect(Internal::CheckNewVersionsJob).not_to have_received(:set)
+  end
+end