chore: Limit the number of articles retrieved by widget (#11095)

The UI displays only six articles, and this update introduces a per_page
parameter to control the number of articles returned per API call. The
value is capped between 1 and 100, with a default fallback if a lower
number is set.

This change is necessary due to high website traffic, where excessive
payloads are returned without adding value.

**Changes:** 
- Add index to status, account_id, portal_id, views.
- Add per_page param in the API.
- Update the code in the frontend to fetch only 6

app/models/article.rb

@@ -23,9 +23,13 @@
 #
 # Indexes
 #
+#  index_articles_on_account_id             (account_id)
 #  index_articles_on_associated_article_id  (associated_article_id)
 #  index_articles_on_author_id              (author_id)
+#  index_articles_on_portal_id              (portal_id)
 #  index_articles_on_slug                   (slug) UNIQUE
+#  index_articles_on_status                 (status)
+#  index_articles_on_views                  (views)
 #
 class Article < ApplicationRecord
   include PgSearch::Model