feat(linear): Support refresh tokens and migrate legacy OAuth tokens (#13721)

Linear is deprecating long-lived OAuth2 access tokens (valid for 10
years) in favor of short-lived access tokens with refresh tokens.
Starting October 1, 2025, all new OAuth2 apps will default to refresh
tokens. Linear will no longer issue long-lived access tokens. Please
read more details
[here](https://linear.app/developers/oauth-2-0-authentication#migrate-to-using-refresh-tokens)
We currently use long-lived tokens in our Linear integration (valid for
up to 10 years). To remain compatible, this PR ensures compatibility by
supporting refresh-token-based auth and migrating existing legacy
tokens.

Fixes
https://linear.app/chatwoot/issue/CW-5541/migrate-linear-oauth2-integration-to-support-refresh-tokens

app/controllers/api/v1/accounts/integrations/linear_controller.rb

@@ -126,7 +126,7 @@ class Api::V1::Accounts::Integrations::LinearController < Api::V1::Accounts::Bas
     return unless @hook&.access_token
 
     begin
-      linear_client = Linear.new(@hook.access_token)
+      linear_client = Linear.new(@hook.access_token, refresh_token: @hook.settings&.[]('refresh_token'))
       linear_client.revoke_token
     rescue StandardError => e
       Rails.logger.error "Failed to revoke Linear token: #{e.message}"