Full rewrite of struts2-easyui-system from Struts2/Spring/Hibernate to
Spring Boot 3.4.3 (Java 21) + React 18 (TypeScript).

Features:
- JWT-based authentication and RBAC (roles/authorities)
- Equipment and document management with Excel export
- AOP access logging and user statistics charts
- Dynamic sidebar menu loaded from database
- Online user tracking (stateless JWT)
- Docker Compose production deployment (MySQL 8 + Spring Boot + Nginx)
- Flyway schema management (V1–V3 migrations)
- 110 passing tests (63 backend + 15 frontend + 32 E2E)