perf: reduce presence update frequency and fix background tab throttling (#13726)

## Description
Reduces the frequency of update_presence WebSocket calls from the live
chat widget and fixes agents appearing offline when the dashboard is in
a background tab.

## Fixes # (issue)
https://github.com/chatwoot/chatwoot/issues/13720

## Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)


## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

spec/lib/online_status_tracker_spec.rb

@@ -42,7 +42,7 @@ describe OnlineStatusTracker do
       described_class.update_presence(account.id, 'Contact', online_contact.id)
       # creating a stale record for offline contact presence
       Redis::Alfred.zadd(format(Redis::Alfred::ONLINE_PRESENCE_CONTACTS, account_id: account.id),
-                         (Time.zone.now - (OnlineStatusTracker::PRESENCE_DURATION + 20)).to_i, offline_contact.id)
+                         (Time.zone.now - (OnlineStatusTracker::CONTACT_PRESENCE_DURATION + 20)).to_i, offline_contact.id)
     end
 
     it 'returns only the online contact ids with presence' do