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/app/admin/media/MediaLibrary.tsx

@@ -179,7 +179,8 @@ export default function MediaLibrary({
       <Modal
         open={active !== null}
         onClose={() => setActive(null)}
-        title={active?.name ?? ""}
+        title={<span className="break-all">{active?.name ?? ""}</span>}
+        ariaLabel={active?.name ?? ""}
         description={active ? `${active.category_name}${active.uploader ? ` · 上传者 ${active.uploader}` : ""}` : undefined}
         maxWidthClass="max-w-2xl"
         dismissOnOverlay
@@ -218,6 +219,14 @@ export default function MediaLibrary({
                 ["格式", active.mime],
                 ["上传者", active.uploader || "—"],
                 ["时间", formatTime(active.uploaded_at)],
+                ...(active.ref_count && active.ref_count > 1
+                  ? [
+                      [
+                        "引用",
+                        `${active.ref_count} 次上传 · 去重节省 ${formatBytes(active.size * (active.ref_count - 1))}`,
+                      ],
+                    ]
+                  : []),
               ].map(([k, v]) => (
                 <div key={k} className="flex items-baseline gap-2 min-w-0">
                   <dt className="meta shrink-0 w-11 text-right">{k}</dt>