feat: add custom publish time and last updated time display

- Add custom publish time field to article create/edit forms
  - Support datetime-local input for manual time setting
  - Auto-set on first publish if left blank
  - Works for both admin and user article forms

- Display last updated time on article detail page
  - Show both published time and last updated time
  - Auto-maintained by GORM on each update
  - Format: YYYY-MM-DD HH:MM

- Add i18n support for new fields
  - article_published_at: Published Time / 发布时间
  - article_published_at_hint: Leave blank to auto-set on publish / 留空则在发布时自动设置
  - article_last_updated: Last Updated / 最后更新

- Update handlers and templates
  - handlers/article.go: Add parsePublishedAt/formatPublishedAt functions
  - handlers/home.go: Add formatUpdateTime function
  - handlers/my_articles.go: Support custom publish time in user articles
  - templates: Add datetime-local inputs and time display

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

handlers/article.go

@@ -69,29 +69,31 @@ func fallbackSlug(id uint) string {
 // articleForm holds the parsed article form fields, shared by the create and
 // edit handlers and their validation-error repopulation paths.
 type articleForm struct {
-	Title        string
-	Slug         string
-	Summary      string
-	Content      string
-	Cover        string
-	StatusStr    string
-	IsTop        bool
-	Action       string // form action URL
-	TitleText    string // page heading text (create vs edit)
-	ArticleID    uint   // existing article ID (edit page); 0 on create
-	SessionToken string // pending-attachment ownership token (create page)
+	Title         string
+	Slug          string
+	Summary       string
+	Content       string
+	Cover         string
+	StatusStr     string
+	IsTop         bool
+	PublishedAt   string // datetime-local format: "2006-01-02T15:04"
+	Action        string // form action URL
+	TitleText     string // page heading text (create vs edit)
+	ArticleID     uint   // existing article ID (edit page); 0 on create
+	SessionToken  string // pending-attachment ownership token (create page)
 }
 
 // parseArticleForm reads and trims the article form fields from the request.
 func parseArticleForm(c *gin.Context) articleForm {
 	return articleForm{
-		Title:     strings.TrimSpace(c.PostForm("title")),
-		Slug:      strings.TrimSpace(c.PostForm("slug")),
-		Summary:   strings.TrimSpace(c.PostForm("summary")),
-		Content:   strings.TrimSpace(c.PostForm("content")),
-		Cover:     strings.TrimSpace(c.PostForm("cover")),
-		StatusStr: c.PostForm("status"),
-		IsTop:     c.PostForm("is_top") == "1",
+		Title:       strings.TrimSpace(c.PostForm("title")),
+		Slug:        strings.TrimSpace(c.PostForm("slug")),
+		Summary:     strings.TrimSpace(c.PostForm("summary")),
+		Content:     strings.TrimSpace(c.PostForm("content")),
+		Cover:       strings.TrimSpace(c.PostForm("cover")),
+		StatusStr:   c.PostForm("status"),
+		IsTop:       c.PostForm("is_top") == "1",
+		PublishedAt: strings.TrimSpace(c.PostForm("published_at")),
 	}
 }
 
@@ -105,6 +107,7 @@ func applyFormToData(data gin.H, f articleForm) {
 	data["FormCover"] = f.Cover
 	data["FormStatus"] = f.StatusStr
 	data["FormIsTop"] = f.IsTop
+	data["FormPublishedAt"] = f.PublishedAt
 	data["FormAction"] = f.Action
 	data["FormTitleText"] = f.TitleText
 	data["FormArticleID"] = f.ArticleID
@@ -154,6 +157,29 @@ func statusFromForm(statusStr string) int {
 	return models.ArticleDraft
 }
 
+// parsePublishedAt parses the datetime-local format ("2006-01-02T15:04") from
+// the form into a time.Time pointer. Returns nil if the string is empty or invalid.
+func parsePublishedAt(publishedAtStr string) *time.Time {
+	if publishedAtStr == "" {
+		return nil
+	}
+	// datetime-local format: "2006-01-02T15:04"
+	t, err := time.ParseInLocation("2006-01-02T15:04", publishedAtStr, time.Local)
+	if err != nil {
+		return nil
+	}
+	return &t
+}
+
+// formatPublishedAt formats a time.Time pointer into datetime-local format for the form.
+// Returns empty string if the pointer is nil.
+func formatPublishedAt(t *time.Time) string {
+	if t == nil {
+		return ""
+	}
+	return t.Local().Format("2006-01-02T15:04")
+}
+
 // ArticleCreatePage renders the article creation form.
 func ArticleCreatePage(db *gorm.DB) gin.HandlerFunc {
 	return func(c *gin.Context) {
@@ -205,7 +231,11 @@ func ArticleCreate(db *gorm.DB) gin.HandlerFunc {
 		}
 
 		var publishedAt *time.Time
-		if status == models.ArticlePublished {
+		if f.PublishedAt != "" {
+			// User provided a custom published time
+			publishedAt = parsePublishedAt(f.PublishedAt)
+		} else if status == models.ArticlePublished {
+			// Auto-stamp with current time if publishing without custom time
 			now := time.Now()
 			publishedAt = &now
 		}
@@ -271,16 +301,17 @@ func ArticleEditPage(db *gorm.DB) gin.HandlerFunc {
 		}
 
 		renderArticleForm(c, db, articleForm{
-			Title:     article.Title,
-			Slug:      article.Slug,
-			Summary:   article.Summary,
-			Content:   article.Content,
-			Cover:     article.Cover,
-			StatusStr: strconv.Itoa(article.Status),
-			IsTop:     article.IsTop,
-			Action:    "/admin/articles/" + id + "/edit",
-			TitleText: tr["article_edit_title"],
-			ArticleID: article.ID,
+			Title:       article.Title,
+			Slug:        article.Slug,
+			Summary:     article.Summary,
+			Content:     article.Content,
+			Cover:       article.Cover,
+			StatusStr:   strconv.Itoa(article.Status),
+			IsTop:       article.IsTop,
+			PublishedAt: formatPublishedAt(article.PublishedAt),
+			Action:      "/admin/articles/" + id + "/edit",
+			TitleText:   tr["article_edit_title"],
+			ArticleID:   article.ID,
 		}, "")
 	}
 }
@@ -319,12 +350,19 @@ func ArticleUpdate(db *gorm.DB) gin.HandlerFunc {
 
 		newStatus := statusFromForm(f.StatusStr)
 
-		// Stamp the publish time the first time an article is published.
-		wasPublished := article.Status == models.ArticlePublished
-		var publishedAt *time.Time = article.PublishedAt
-		if newStatus == models.ArticlePublished && !wasPublished && publishedAt == nil {
-			now := time.Now()
-			publishedAt = &now
+		// Handle published_at: use form value if provided, otherwise auto-stamp on first publish.
+		var publishedAt *time.Time
+		if f.PublishedAt != "" {
+			// User provided a custom published time
+			publishedAt = parsePublishedAt(f.PublishedAt)
+		} else {
+			// Auto-stamp the publish time the first time an article is published.
+			wasPublished := article.Status == models.ArticlePublished
+			publishedAt = article.PublishedAt
+			if newStatus == models.ArticlePublished && !wasPublished && publishedAt == nil {
+				now := time.Now()
+				publishedAt = &now
+			}
 		}
 
 		updates := map[string]interface{}{