feat: PTY kubectl终端 + 侧边栏对齐修复 + 构建缓存清理

**kubectl WebShell 修复：**
- 引入 github.com/creack/pty 库实现真正的伪终端
- 替换 bash --noediting + TERM=dumb 方案为 PTY-backed bash
- 支持 xterm-256color、窗口自适应、readline 交互
- 修复键盘输入无响应问题

**侧边栏优化：**
- 独立菜单项高度从 py-1.5 改为 h-8，与父菜单对齐
- 独立菜单图标从 h-3 w-3 改为 h-3.5 w-3.5，统一 14px

**构建优化：**
- run.sh docker up 增加 docker image prune -f 清理悬空镜像
- 每次部署自动清理 builder cache + dangling images

**认证修复（历史）：**
- Token 存储：Zustand + localStorage 双写，http.ts 双源 fallback
- YamlViewer/DeploymentDetail token 来源统一为 Zustand store

backend/go.sum

@@ -14,6 +14,8 @@ github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XL
 github.com/chenzhuoyu/base64x v0.0.0-20211019084208-fb5309c8db06/go.mod h1:DH46F32mSOjUmXrMHnKwZdA8wcEefY7UVqBKYGjpdQY=
 github.com/chenzhuoyu/base64x v0.0.0-20221115062448-fe3a3abad311 h1:qSGYFH7+jGhDF8vLC+iwCD4WpbV1EBDSzWkJODFLams=
 github.com/chenzhuoyu/base64x v0.0.0-20221115062448-fe3a3abad311/go.mod h1:b583jCggY9gE99b6G5LEC39OIiVsWj+R97kbl5odCEk=
+github.com/creack/pty v1.1.24 h1:bJrF4RRfyJnbTJqzRLHzcGaZK1NeM5kTC9jGgovnR1s=
+github.com/creack/pty v1.1.24/go.mod h1:08sCNb52WyoAwi2QDyzUCTgcvVFhUzewun7wtTfvcwE=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=