feat: 脚本创作+发布+市场体系

- 数据模型新增: title(必填), description(可选), status(draft/published)
- 新增 API: POST /scripts/:id/publish, GET /api/market (搜索+分页+runtime过滤)
- 前端首页重构: 选语言 → CodeMirror 编辑器(8种语言语法高亮) → 标题/描述 → 草稿/发布
- 新增 /market 页面: 浏览已发布脚本, 搜索+过滤+分页
- 详情页新增: 发布按钮(草稿→市场), title/description 展示
- Shell 类运行时显示 source 命令(继承环境变量)
- backend GetSourceCommand 支持 bash/zsh/sh/fish 四种 shell 格式

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/internal/model/script.go

@@ -3,10 +3,14 @@ package model
 import "time"
 
 type Script struct {
-	ID         string    `gorm:"primaryKey;size:8"`
-	Content    string    `gorm:"type:text;not null"`
-	Runtime    string    `gorm:"size:16;not null;index"`
-	AdminToken string    `gorm:"size:64;not null"`
-	ExpiresAt  time.Time `gorm:"not null;index"`
-	CreatedAt  time.Time `gorm:"not null;autoCreateTime"`
-}
+	ID          string     `gorm:"primaryKey;size:8"`
+	Title       string     `gorm:"size:128;not null"`
+	Description string     `gorm:"size:512"`
+	Content     string     `gorm:"type:text;not null"`
+	Runtime     string     `gorm:"size:16;not null;index"`
+	AdminToken  string     `gorm:"size:64;not null"`
+	Status      string     `gorm:"size:16;not null;default:draft;index"`
+	ExpiresAt   time.Time  `gorm:"not null;index"`
+	CreatedAt   time.Time  `gorm:"not null;autoCreateTime"`
+	PublishedAt *time.Time `gorm:"index"`
+}