feat: 站点单页、时间线导入与行级 BBCode 短代码

首页右栏接入单页入口与公告置顶/全部页；Markdown 编辑器支持可视化时间线与 Git 导入；隐藏块改为 [hide]/[timeline] 命名闭合，并修复单页/公告 GORM 更新只改 updated_at 的问题。

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

backend/handler/site_page.go

@@ -0,0 +1,93 @@
+package handler
+
+import (
+	"errors"
+	"net/http"
+	"strconv"
+
+	"github.com/freefire/jiang13-bbs/service"
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+)
+
+// SitePageDetail 公开单页详情（按 slug）
+func (h *Handlers) SitePageDetail(c *gin.Context) {
+	slug := c.Param("slug")
+	p, err := h.SitePage.GetPublishedBySlug(slug)
+	if err != nil {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			c.JSON(http.StatusNotFound, gin.H{"error": "页面不存在"})
+			return
+		}
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "获取页面失败"})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"page": p})
+}
+
+// AdminListSitePages 后台单页列表
+func (h *Handlers) AdminListSitePages(c *gin.Context) {
+	list, err := h.SitePage.ListAll()
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "获取页面失败"})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"pages": nonNilSlice(list)})
+}
+
+// AdminCreateSitePage 新建单页
+func (h *Handlers) AdminCreateSitePage(c *gin.Context) {
+	var in service.SitePageInput
+	if err := c.ShouldBindJSON(&in); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "请求参数无效"})
+		return
+	}
+	p, err := h.SitePage.Create(&in)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+	c.JSON(http.StatusCreated, gin.H{"page": p})
+}
+
+// AdminUpdateSitePage 编辑单页
+func (h *Handlers) AdminUpdateSitePage(c *gin.Context) {
+	id, err := strconv.ParseUint(c.Param("id"), 10, 64)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "无效的页面 ID"})
+		return
+	}
+	var in service.SitePageInput
+	if err := c.ShouldBindJSON(&in); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "请求参数无效"})
+		return
+	}
+	p, err := h.SitePage.Update(uint(id), &in)
+	if err != nil {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			c.JSON(http.StatusNotFound, gin.H{"error": "页面不存在"})
+			return
+		}
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"page": p})
+}
+
+// AdminDeleteSitePage 删除单页
+func (h *Handlers) AdminDeleteSitePage(c *gin.Context) {
+	id, err := strconv.ParseUint(c.Param("id"), 10, 64)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "无效的页面 ID"})
+		return
+	}
+	if err := h.SitePage.Delete(uint(id)); err != nil {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			c.JSON(http.StatusNotFound, gin.H{"error": "页面不存在"})
+			return
+		}
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "删除失败"})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"ok": true})
+}