fix: handle Socket::ResolutionError in browser push notifications (#13957)

## Linear Ticket

https://linear.app/chatwoot/issue/CW-6707/socketresolutionerror-failed-to-open-tcp-connection-to-permanently

https://linear.app/chatwoot/issue/CW-6707/socketresolutionerror-failed-to-open-tcp-connection-to-permanently#comment-14e0f9ff

## Description

Browser push notifications fail with Socket::ResolutionError when the
push subscription endpoint's domain can't be resolved via DNS (e.g.,
defunct push service, transient DNS failure). This error wasn't handled
in handle_browser_push_error, so it fell through to the catch-all else
branch and got reported to Sentry on every notification attempt — 1,637
times in the last 7 days.
The dead subscription was never cleaned up or the error suppressed, so
every subsequent notification for the affected user triggered the same
Sentry alert.
Added Socket::ResolutionError to the existing transient network error
handler alongside Errno::ECONNRESET, Net::OpenTimeout, and
Net::ReadTimeout. The error is logged but not reported to Sentry, and
the subscription is kept intact in case it's a temporary DNS blip.

## Type of change

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

## How Has This Been Tested?

- Verified that Socket::ResolutionError is a subclass of StandardError
and matches the when clause

## 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

Co-authored-by: Vishnu Narayanan <iamwishnu@gmail.com>

app/services/notification/push_notification_service.rb

@@ -79,7 +79,7 @@ class Notification::PushNotificationService
       subscription.destroy!
     when WebPush::TooManyRequests
       Rails.logger.warn "WebPush rate limited for #{user.email} on account #{notification.account.id}: #{error.message}"
-    when Errno::ECONNRESET, Net::OpenTimeout, Net::ReadTimeout
+    when Errno::ECONNRESET, Net::OpenTimeout, Net::ReadTimeout, Socket::ResolutionError
       Rails.logger.error "WebPush operation error: #{error.message}"
     else
       ChatwootExceptionTracker.new(error, account: notification.account).capture_exception