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/components/SiteBrandProvider.tsx

@@ -2,7 +2,7 @@
 
 import { createContext, useContext, useEffect, useMemo, useRef, useState, type ReactNode } from "react";
 import { apiGetSettings, type PublicSettings } from "@/lib/api";
-import { siteDocumentTitle, normalizeBrandLogoFit, normalizeBrandLogoSize, normalizeBrandMark, normalizeFooterLinks } from "@/lib/brand";
+import { siteDocumentTitle, normalizeBrandLogoFit, normalizeBrandLogoSize, normalizeBrandMark, normalizeBrandSloganVisible, normalizeFooterLinks } from "@/lib/brand";
 import { normalizeUrlStyle, type UrlStyle } from "@/lib/urlStyle";
 import { DEFAULT_MOBILE_TABS, normalizeMobileTabs, type MobileTabKey } from "@/lib/mobileTabs";
 import { DEFAULT_HEADER_NAV, normalizeHeaderNav, type HeaderNavItem } from "@/lib/headerNav";
@@ -19,6 +19,7 @@ export type SiteBrand = {
   brand_mark: PublicSettings["brand_mark"];
   brand_logo_size: PublicSettings["brand_logo_size"];
   brand_logo_fit: PublicSettings["brand_logo_fit"];
+  brand_slogan_visible: boolean;
   footer_links: PublicSettings["footer_links"];
   url_style: UrlStyle;
   mobile_tabs: MobileTabKey[];
@@ -38,6 +39,7 @@ function fromSettings(s: PublicSettings): SiteBrand {
     brand_mark: s.brand_mark,
     brand_logo_size: s.brand_logo_size,
     brand_logo_fit: s.brand_logo_fit,
+    brand_slogan_visible: s.brand_slogan_visible,
     footer_links: s.footer_links,
     url_style: s.url_style,
     mobile_tabs: s.mobile_tabs,
@@ -56,6 +58,7 @@ function sameBrand(a: SiteBrand, b: SiteBrand): boolean {
     a.brand_mark === b.brand_mark &&
     a.brand_logo_size === b.brand_logo_size &&
     a.brand_logo_fit === b.brand_logo_fit &&
+    a.brand_slogan_visible === b.brand_slogan_visible &&
     a.url_style === b.url_style &&
     JSON.stringify(a.footer_links) === JSON.stringify(b.footer_links) &&
     JSON.stringify(a.mobile_tabs) === JSON.stringify(b.mobile_tabs) &&
@@ -108,6 +111,7 @@ export function useSiteBrand(): SiteBrand {
       brand_mark: "image_text",
       brand_logo_size: "sq",
       brand_logo_fit: "contain",
+      brand_slogan_visible: true,
       footer_links: [],
       url_style: "default",
       mobile_tabs: [...DEFAULT_MOBILE_TABS],
@@ -159,6 +163,10 @@ export default function SiteBrandProvider({
         brand_mark: normalizeBrandMark(raw.brand_mark ?? prev.brand_mark),
         brand_logo_size: normalizeBrandLogoSize(raw.brand_logo_size ?? prev.brand_logo_size),
         brand_logo_fit: normalizeBrandLogoFit(raw.brand_logo_fit ?? prev.brand_logo_fit),
+        brand_slogan_visible:
+          raw.brand_slogan_visible !== undefined
+            ? normalizeBrandSloganVisible(raw.brand_slogan_visible)
+            : prev.brand_slogan_visible,
         footer_links: Array.isArray(raw.footer_links)
           ? normalizeFooterLinks(raw.footer_links)
           : prev.footer_links,