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/javascript/dashboard/i18n/locale/en/helpCenter.json

@@ -700,9 +700,27 @@
           "MAKE_DEFAULT": "Make default",
           "MOVE_TO_DRAFT": "Move to draft",
           "PUBLISH_LOCALE": "Publish locale",
+          "CUSTOMIZE_CONTENT": "Localize content",
           "DELETE": "Delete"
         }
       },
+      "CONTENT_DIALOG": {
+        "TITLE": "Localize content",
+        "DESCRIPTION": "Set values specific to this locale. Anything left blank falls back to the default locale.",
+        "NAME": {
+          "LABEL": "Name"
+        },
+        "PAGE_TITLE": {
+          "LABEL": "Page title"
+        },
+        "HEADER_TEXT": {
+          "LABEL": "Header text"
+        },
+        "API": {
+          "SUCCESS_MESSAGE": "Locale content updated successfully",
+          "ERROR_MESSAGE": "Unable to update locale content. Try again."
+        }
+      },
       "ADD_LOCALE_DIALOG": {
         "TITLE": "Add a new locale",
         "DESCRIPTION": "Select the language in which this article will be written. This will be added to your list of translations, and you can add more later.",