feat: add --uninstall support to install script

- Add --uninstall flag to remove installed components
- List items to be removed before confirmation
- Remove pass_mgr binary, skills modules, and env config
- Preserve admin key directory (warns user to remove manually)
- Update PROJECT_PLAN.md with uninstall usage

PROJECT_PLAN.md

@@ -286,6 +286,12 @@ node install.mjs --build-only
 
 # 跳过依赖检测
 node install.mjs --skip-check
+
+# 卸载
+node install.mjs --uninstall
+
+# 从指定路径卸载
+node install.mjs --uninstall --prefix /usr/local
 ```
 
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