feat: 媒体库 blob 去重存储与品牌/注册等前端调整

新增：
- blob_store 二进制去重存储 + blob_dedup 测试

其它：
- 后端 settings/auth/media_library/upload/operations 服务与 handler 调整
- 前端品牌（BrandLockup/BrandCropModal/BrandSeoPanel）、注册、媒体库、分析详情页、Header/SiteChrome 等更新

frontend/lib/api.ts

@@ -2,6 +2,7 @@ import {
   normalizeBrandLogoFit,
   normalizeBrandLogoSize,
   normalizeBrandMark,
+  normalizeBrandSloganVisible,
   normalizeBrandURL,
   normalizeFooterLinks,
   normalizeKeywords,
@@ -1041,6 +1042,8 @@ export interface PublicSettings {
   brand_logo_size: BrandLogoSize;
   /** 图槽铺法：cover 填充 / contain 适应 / repeat 平铺 / stretch 拉伸 */
   brand_logo_fit: BrandLogoFit;
+  /** 标语是否在页眉显示；缺省 true */
+  brand_slogan_visible: boolean;
   footer_links: FooterLink[];
   allow_register: boolean;
   /** 全站是否开放评论；关闭后前台不展示评论能力 */
@@ -1144,6 +1147,7 @@ const DEFAULT_PUBLIC_SETTINGS: PublicSettings = {
   brand_mark: "image_text",
   brand_logo_size: "sq",
   brand_logo_fit: "contain",
+  brand_slogan_visible: true,
   footer_links: [],
   allow_register: true,
   allow_comments: true,
@@ -1235,6 +1239,7 @@ function normalizePublicSettings(data: Partial<PublicSettings> | null | undefine
     brand_mark: normalizeBrandMark(data?.brand_mark),
     brand_logo_size: normalizeBrandLogoSize(data?.brand_logo_size),
     brand_logo_fit: normalizeBrandLogoFit(data?.brand_logo_fit),
+    brand_slogan_visible: normalizeBrandSloganVisible(data?.brand_slogan_visible),
     footer_links: normalizeFooterLinks(data?.footer_links),
     allow_register: data?.allow_register !== false,
     allow_comments: data?.allow_comments !== false,
@@ -3760,6 +3765,7 @@ export type UpdateSiteSettingsBody = {
   brand_mark?: BrandMark;
   brand_logo_size?: BrandLogoSize;
   brand_logo_fit?: BrandLogoFit;
+  brand_slogan_visible?: boolean;
   footer_links?: FooterLink[];
   allow_register?: boolean;
   allow_comments?: boolean;
@@ -4825,6 +4831,7 @@ export interface MediaLibraryItem {
   height: number;
   uploader?: string;
   uploaded_at?: string;
+  ref_count?: number; // 引用计数（>1 表示内容相同的重复上传共享此文件）
   source_url?: string; // 来源回链（帖子/评论锚点/用户主页）
   source_label?: string; // 来源描述（如：帖子《…》下的评论）
 }