1. Add 登陆功能

2. 调整字体大小
3. 新增部分功能

backend/app/api/dependencies/__init__.py

@@ -0,0 +1,5 @@
+"""FastAPI dependency functions for authentication and authorisation.
+
+Import `get_current_user` or `require_role` into route modules to protect
+endpoints. Both use the shared JWTHandler wired through bootstrap.
+"""