chore(ci, dto): update build workflow and enhance post DTOs

- Added NODE_NO_WARNINGS environment variable to build and deploy workflows.
- Upgraded actions/upload-artifact and actions/download-artifact to version 4 in the build workflow.
- Introduced ContentEditedAt field in PostResponse and PostDetailResponse DTOs to track content modification timestamps.
- Updated post conversion functions to include ContentEditedAt in responses.
- Ensured ContentEditedAt is set during post updates in the repository.

internal/model/post.go

@@ -60,6 +60,8 @@ type Post struct {
 	// 时间戳
 	CreatedAt time.Time `json:"created_at" gorm:"autoCreateTime;index:idx_posts_status_created,priority:2,sort:desc;index:idx_posts_user_status_created,priority:3,sort:desc;index:idx_posts_hot_score_created,priority:2,sort:desc"`
 	UpdatedAt time.Time `json:"updated_at" gorm:"autoUpdateTime:false"`
+	// ContentEditedAt 仅在实际修改标题/正文/图片时更新，供前端展示「已编辑」；与统计类更新解耦
+	ContentEditedAt *time.Time `json:"content_edited_at,omitempty" gorm:"column:content_edited_at"`
 }
 
 // BeforeCreate 创建前生成UUID