📝 docs(commands): add auth-jumpback command documentation

- document the auth-jumpback command for login source page jumpback functionality
- specify prerequisite check via auth-check command
- provide usage example for automatic page return after login

.roo/commands/auth-jumpback-增加登录来源页回跳.md

@@ -0,0 +1,8 @@
+---
+description: "增加登录来源页回跳功能指令"
+---
+先 执行 .roo/commands/auth-check-认证相关文件检查.md
+
+然后
+增加 登录来源页回跳功能
+例始打开 /mobile/stock?classroom=J001&code=000001 时，判断未登录，去登录，登录后自动跳回这个页面