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

lib/online_status_tracker.rb

@@ -1,6 +1,8 @@
 class OnlineStatusTracker
   # NOTE: You can customise the environment variable to keep your agents/contacts as online for longer
   PRESENCE_DURATION = ENV.fetch('PRESENCE_DURATION', 20).to_i.seconds
+  # Widget pings every 60s, so contacts need a longer presence window
+  CONTACT_PRESENCE_DURATION = ENV.fetch('CONTACT_PRESENCE_DURATION', 90).to_i.seconds
 
   # presence : sorted set with timestamp as the score & object id as value
 
@@ -11,7 +13,8 @@ class OnlineStatusTracker
 
   def self.get_presence(account_id, obj_type, obj_id)
     connected_time = ::Redis::Alfred.zscore(presence_key(account_id, obj_type), obj_id)
-    connected_time && connected_time > (Time.zone.now - PRESENCE_DURATION).to_i
+    duration = obj_type == 'Contact' ? CONTACT_PRESENCE_DURATION : PRESENCE_DURATION
+    connected_time && connected_time > (Time.zone.now - duration).to_i
   end
 
   def self.presence_key(account_id, type)
@@ -39,7 +42,7 @@ class OnlineStatusTracker
   end
 
   def self.get_available_contact_ids(account_id)
-    range_start = (Time.zone.now - PRESENCE_DURATION).to_i
+    range_start = (Time.zone.now - CONTACT_PRESENCE_DURATION).to_i
     # exclusive minimum score is specified by prefixing (
     # we are clearing old records because this could clogg up the sorted set
     ::Redis::Alfred.zremrangebyscore(presence_key(account_id, 'Contact'), '-inf', "(#{range_start}")