feat(ee): Add a service to fetch website content and prepare a persona of Captain Assistant (#12732)

This PR is the first of many to simplify the process of building an
assistant. The new flow will only require the user’s website. We’ll
automatically crawl it, identify the business name and what the business
does, and then generate a suggested assistant persona, complete with a
proposed name and description.

This service returns the following.
Example: tooljet.com
<img width="795" height="217" alt="Screenshot 2025-10-25 at 2 55 04 PM"
src="https://github.com/user-attachments/assets/9cb3594a-9c9c-4970-a0a1-4c9c8869c193"
/>

Example: replit.com
<img width="797" height="176" alt="Screenshot 2025-10-25 at 2 56 42 PM"
src="https://github.com/user-attachments/assets/6a1b4266-aab6-455f-a5e3-696d3a8243c9"
/>

enterprise/app/services/llm/base_open_ai_service.rb

@@ -1,5 +1,6 @@
 class Llm::BaseOpenAiService
   DEFAULT_MODEL = 'gpt-4o-mini'.freeze
+  attr_reader :client, :model
 
   def initialize
     @client = OpenAI::Client.new(