Fix total_pages calculation to respect X-Per-Page header

The total_pages method was using the hardcoded SEARCH_PER_PAGE constant
instead of the dynamic search_page_size value from the X-Per-Page header.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/controllers/api/v1/search_controller.rb

@@ -275,7 +275,8 @@ module Api
       private
 
       def total_pages(count)
-        count.to_f / SEARCH_PER_PAGE > 1 ? (count.to_f / SEARCH_PER_PAGE).ceil : 1
+        per_page = search_page_size
+        (count.to_f / per_page).ceil
       end
 
       # Specify whitelisted properties that can be modified.