feat(nav): Implement historical NAV tracking and enhance product API

- Added `list_nav_history` method in `CoreReadOnlyRepository` to retrieve historical NAV data for products over a specified number of days.
- Introduced `get_nav_history` endpoint in `product_service` to return historical NAV sequences, improving product data accessibility.
- Updated `products.py` to include new API endpoint for fetching NAV history, ensuring compliance with access control.
- Enhanced `ready.py` to include a health check for the new functionality, ensuring system readiness.
- Updated documentation to reflect the new testing baseline of 833 passed tests, indicating improved stability and functionality across the application.

This update significantly enhances the product API by providing access to historical NAV data, improving user insights into product performance.

docs/superpowers/specs/2026-09-11-architecture-governance-course-design.md

@@ -23,3 +23,5 @@ Vibe coder：能指挥 AI，需理解 ADR、不变量（architecture decisions
 ## 与现有课关系
 
 不替换 `jinrong-module-*`；从 `docs/course/index.html` 链入。
+
+**答辩口径：** **代理人 Agent 未完整接入**（顾问线无独立深编排 · T-20 未做 · 主 Demo 不含顾问 Chat 深演示）。