feat(help-center): support per-locale portal title, name & header (#14642)

Portals can now override their name, page title and header text per
locale, with a fallback chain of locale override → default locale → base
value. Overrides are stored under portal.config.locale_translations and
validated with a JSON schema.

Editing is exposed as a "Localize content" action in each non-default
locale's menu on the Locale page, and all public-facing portal views
(classic + documentation layouts) render the localized values. The live
chat widget is also loaded in the active portal locale.


<img width="494" height="395" alt="Screenshot 2026-06-03 at 2 48 59 PM"
src="https://github.com/user-attachments/assets/e55a06e8-f20f-4d8a-9352-92fde28a9a19"
/>



https://github.com/user-attachments/assets/f5affbd2-7ad4-415a-b376-57c759fc2aaa

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/controllers/api/v1/accounts/portals_controller.rb

@@ -80,10 +80,15 @@ class Api::V1::Accounts::PortalsController < Api::V1::Accounts::BaseController
       :id, :color, :custom_domain, :header_text, :homepage_link,
       :name, :page_title, :slug, :archived,
       { config: [:default_locale, :layout, { allowed_locales: [] }, { draft_locales: [] },
-                 { social_profiles: %i[facebook x instagram linkedin youtube tiktok github whatsapp] }] }
+                 { social_profiles: %i[facebook x instagram linkedin youtube tiktok github whatsapp] },
+                 { locale_translations: locale_translation_keys.index_with { %i[name page_title header_text] } }] }
     )
   end
 
+  def locale_translation_keys
+    params.dig(:portal, :config, :locale_translations)&.keys || []
+  end
+
   def live_chat_widget_params
     permitted_params = params.permit(:inbox_id)
     return {} unless permitted_params.key?(:inbox_id)