feat: 全站评论开关，并统一后台表单控件

关闭评论后前台隐藏评论能力；外观/设置/公告改用 AdminField 与 Stepper。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/handler/user.go

@@ -151,6 +151,21 @@ func (h *Handlers) UserComments(c *gin.Context) {
 		return
 	}
 
+	if allow, err := h.Setting.AllowComments(); err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "评论暂时不可用"})
+		return
+	} else if !allow {
+		page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
+		size, _ := strconv.Atoi(c.DefaultQuery("size", "20"))
+		c.JSON(http.StatusOK, gin.H{
+			"comments": []any{},
+			"total":    0,
+			"page":     page,
+			"size":     size,
+		})
+		return
+	}
+
 	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
 	size, _ := strconv.Atoi(c.DefaultQuery("size", "20"))