feat(threshold): Implement customer loss threshold configuration and notification system

- Added `ThresholdRepository` for managing customer loss threshold configurations and notifications.
- Introduced `threshold_service` to handle loss threshold alerts based on customer portfolio performance.
- Enhanced `customer_prompts` to include new intent for querying product net values.
- Updated `customer_service` to integrate new threshold alert functionality into existing workflows.
- Implemented `sanitize_postprocess` for improved compliance handling in customer interactions.
- Enhanced course documentation to reflect updates in advisor training modules and interactive elements.

This update significantly improves the customer experience by providing proactive loss threshold notifications and enhancing the overall service framework.

docs/course/jinrong-module-platform/modules/02-auth-flow.html

@@ -38,7 +38,7 @@
           <div class="chat-message" data-msg="1" data-sender="api" style="display:none">
             <div class="chat-avatar" style="background: #5A9DB8">🚪</div>
             <div class="chat-bubble">
-              <span class="chat-sender" style="color: #5A9DB8">customers.py</span>
+              <span class="chat-sender" style="color: #5A9DB8">平台客户 REST 薄路由（customers.py）</span>
               <p>Depends(get_platform_auth_context) → JWT 验签 OK<br>assert_platform_customer_access：STAFF-10086 名下有 CUST-1001 ✓</p>
             </div>
           </div>