Make search parameter optional for search endpoints

Allow search endpoints to work without the 'search' key in the request body.
When no search key is provided, return an empty hash to show all items.

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

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

app/controllers/api/v1/search_controller.rb

@@ -280,6 +280,7 @@ module Api
 
       # Specify whitelisted properties that can be modified.
       def search_params
+        return {} unless params[:search].present?
         params.require(:search).permit!
       end
     end