feat: 新增发布日期自选、站点 Logo、回收站清空等十项改进

- 编辑页标题改 filled 变体；标签改 tags 选择器（可勾选既有/输入新建）
- 笔记发布日期可自选（schema v2 新增 published_at 并回填），前台展示发布日期
- 登录页移除「请输入管理密码以继续」「连续失败将被暂时锁定」文案
- 站点设置每页条数收敛为 10/20/30/50 选择器，后端白名单同源校验
- 站点设置两卡片宽屏左右/窄屏上下；修改密码按钮改常规大小
- 后台各页顶栏固定高度，切换页面不再抖动
- 站点 Logo：settings 新增 site_logo（站内路径），gc/孤儿清单豁免 Logo 图片，
  博客 header 站点名前展示，设置页支持上传/更换/清除
- 回收站右上角一键清空（DELETE /api/admin/trash，含确认弹窗）
- pn init 写入 Markdown 语法示例文档（slug welcome，公开）与程序生成的示例图片

internal/httpapi/admin.go

@@ -27,16 +27,17 @@ import (
 
 // adminNoteItem 管理列表项（不含全文）。
 type adminNoteItem struct {
-	ID        int64    `json:"id"`
-	Slug      string   `json:"slug"`
-	Title     string   `json:"title"`
-	Summary   string   `json:"summary"`
-	Status    string   `json:"status"`
-	Tags      []string `json:"tags"`
-	Pinned    bool     `json:"pinned"`
-	DeletedAt *int64   `json:"deleted_at,omitempty"`
-	CreatedAt int64    `json:"created_at"`
-	UpdatedAt int64    `json:"updated_at"`
+	ID          int64    `json:"id"`
+	Slug        string   `json:"slug"`
+	Title       string   `json:"title"`
+	Summary     string   `json:"summary"`
+	Status      string   `json:"status"`
+	Tags        []string `json:"tags"`
+	Pinned      bool     `json:"pinned"`
+	DeletedAt   *int64   `json:"deleted_at,omitempty"`
+	CreatedAt   int64    `json:"created_at"`
+	UpdatedAt   int64    `json:"updated_at"`
+	PublishedAt int64    `json:"published_at"`
 }
 
 func toAdminItem(n *store.Note) adminNoteItem {
@@ -44,6 +45,7 @@ func toAdminItem(n *store.Note) adminNoteItem {
 		ID: n.ID, Slug: n.Slug, Title: n.Title, Summary: n.Summary,
 		Status: n.Status, Tags: n.Tags, Pinned: n.Pinned,
 		DeletedAt: n.DeletedAt, CreatedAt: n.CreatedAt, UpdatedAt: n.UpdatedAt,
+		PublishedAt: n.PublishedAt,
 	}
 }
 
@@ -61,15 +63,16 @@ func (s *Server) handleAdminNotes(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, map[string]any{"items": items, "total": len(items)})
 }
 
-// notePayload 笔记写请求体。
+// notePayload 笔记写请求体。PublishedAt 为发布日期（Unix 秒）；nil = 创建取当前时刻 / 更新保持不变。
 type notePayload struct {
-	Title   string   `json:"title"`
-	Slug    string   `json:"slug"`
-	Summary string   `json:"summary"`
-	Content string   `json:"content"`
-	Status  string   `json:"status"`
-	Tags    []string `json:"tags"`
-	Pinned  bool     `json:"pinned"`
+	Title       string   `json:"title"`
+	Slug        string   `json:"slug"`
+	Summary     string   `json:"summary"`
+	Content     string   `json:"content"`
+	Status      string   `json:"status"`
+	Tags        []string `json:"tags"`
+	Pinned      bool     `json:"pinned"`
+	PublishedAt *int64   `json:"published_at"`
 }
 
 func (p *notePayload) validate() (string, string) { // 返回 (错误码, 消息)
@@ -106,10 +109,14 @@ func (s *Server) handleAdminNoteCreate(w http.ResponseWriter, r *http.Request) {
 	if strings.TrimSpace(summary) == "" {
 		summary = markdown.Summary(p.Content, 200)
 	}
+	publishedAt := now
+	if p.PublishedAt != nil && *p.PublishedAt > 0 {
+		publishedAt = *p.PublishedAt
+	}
 	n := &store.Note{
 		Slug: slug, Title: strings.TrimSpace(p.Title), Summary: summary,
 		Content: p.Content, Status: p.Status, Tags: store.NormalizeTags(p.Tags),
-		Pinned: p.Pinned, CreatedAt: now, UpdatedAt: now,
+		Pinned: p.Pinned, PublishedAt: publishedAt, CreatedAt: now, UpdatedAt: now,
 	}
 	id, err := s.st.CreateNote(n)
 	if err != nil {
@@ -203,6 +210,9 @@ func (s *Server) handleAdminNoteUpdate(w http.ResponseWriter, r *http.Request) {
 	n.Tags = store.NormalizeTags(p.Tags)
 	n.Pinned = p.Pinned
 	n.Content = p.Content
+	if p.PublishedAt != nil && *p.PublishedAt > 0 {
+		n.PublishedAt = *p.PublishedAt
+	}
 	if strings.TrimSpace(p.Summary) == "" {
 		n.Summary = markdown.Summary(p.Content, 200)
 	} else {
@@ -253,6 +263,17 @@ func (s *Server) handleAdminTrash(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, map[string]any{"items": items, "total": len(items)})
 }
 
+// handleAdminTrashEmpty DELETE /api/admin/trash：清空回收站（物理删除全部，§6.2）。
+func (s *Server) handleAdminTrashEmpty(w http.ResponseWriter, r *http.Request) {
+	n, err := s.st.EmptyTrash()
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "internal", "内部错误")
+		return
+	}
+	s.log.Info("admin_action", "op", "trash.empty", "count", n)
+	writeJSON(w, http.StatusOK, map[string]any{"ok": true, "deleted": n})
+}
+
 // handleAdminTrashRestore POST /api/admin/trash/{id}/restore：恢复（清空 deleted_at）。
 func (s *Server) handleAdminTrashRestore(w http.ResponseWriter, r *http.Request) {
 	id, ok := pathID(r)
@@ -397,6 +418,7 @@ type settingsDTO struct {
 	SiteDesc  *string `json:"site_desc"`
 	PageSize  *int    `json:"page_size"`
 	BeianNo   *string `json:"beian_no"`
+	SiteLogo  *string `json:"site_logo"`
 }
 
 // handleAdminSettingsGet GET /api/admin/settings：白名单三键；永不序列化 admin_password_hash。
@@ -415,7 +437,7 @@ func (s *Server) handleAdminSettingsPut(w http.ResponseWriter, r *http.Request)
 	dec.DisallowUnknownFields()
 	var dto settingsDTO
 	if err := dec.Decode(&dto); err != nil {
-		writeError(w, http.StatusBadRequest, "bad_request", "包含未知字段或类型不合法（白名单：site_title/site_desc/page_size/beian_no）")
+		writeError(w, http.StatusBadRequest, "bad_request", "包含未知字段或类型不合法（白名单：site_title/site_desc/page_size/beian_no/site_logo）")
 		return
 	}
 	if dto.SiteTitle != nil {
@@ -440,8 +462,8 @@ func (s *Server) handleAdminSettingsPut(w http.ResponseWriter, r *http.Request)
 		}
 	}
 	if dto.PageSize != nil {
-		if *dto.PageSize < 1 || *dto.PageSize > 100 {
-			writeError(w, http.StatusBadRequest, "bad_request", "page_size ∈ [1,100]")
+		if !store.ValidPageSize(*dto.PageSize) {
+			writeError(w, http.StatusBadRequest, "bad_request", "page_size 仅支持 10/20/30/50")
 			return
 		}
 		if err := s.st.SetSetting(store.KeyPageSize, strconv.Itoa(*dto.PageSize)); err != nil {
@@ -460,6 +482,18 @@ func (s *Server) handleAdminSettingsPut(w http.ResponseWriter, r *http.Request)
 			return
 		}
 	}
+	if dto.SiteLogo != nil {
+		// 仅收站内绝对路径（如 /api/images/1）：CSP img-src 'self'，外链图片本来就无法展示
+		v := strings.TrimSpace(*dto.SiteLogo)
+		if v != "" && (len(v) > 500 || strings.ContainsAny(v, " \t\r\n\"'\\") || !strings.HasPrefix(v, "/")) {
+			writeError(w, http.StatusBadRequest, "bad_request", "站点 Logo 须为站内绝对路径（如 /api/images/1）或留空")
+			return
+		}
+		if err := s.st.SetSetting(store.KeySiteLogo, v); err != nil {
+			writeError(w, http.StatusInternalServerError, "internal", "内部错误")
+			return
+		}
+	}
 	// admin_password_hash 不可经此接口写入（§9.3）：不在白名单结构体中，天然拒绝。
 	s.log.Info("admin_action", "op", "settings.update")
 	ss, err := s.st.GetSiteSettings()