fix(web): 项目主图标统一替换为昔涟3rd_Form-Cyrene-3F-Q-Happy-1.png

- favicon/apple-touch-icon (index.html)
- PWA manifest 图标 (manifest.json)
- PWA precache (sw.js)
- 用户端侧栏品牌头像 (Nav.tsx)
- 管理面板顶栏品牌头像 (AdminApp.tsx)
- 删除已被替换的 icon.svg 残留引用

frontend/web/src/admin/AdminApp.tsx

@@ -138,7 +138,7 @@ function AdminTopBar({ section, onMenu }: { section: AdminSectionId; onMenu?: ()
         </button>
       ) : null}
       <div className="flex min-w-0 items-center gap-2">
-        <img src="/images/Cyrene_Avatar/2nd_Form/Cyrene-2F-N-Happy-1-192x192.png" alt="Cyrene" className="h-7 w-7 shrink-0 rounded-full object-cover" />
+        <img src="/images/Cyrene_Avatar/3rd_Form/Cyrene-3F-Q-Happy-1.png" alt="Cyrene" className="h-7 w-7 shrink-0 rounded-full object-cover" />
         <div className="min-w-0 leading-tight">
           <div className="truncate whitespace-nowrap text-sm font-semibold">Cyrene · 管理面板</div>
           <div className="truncate whitespace-nowrap text-[11px] text-[var(--mu-text-lo)]">{meta?.label ?? "仪表盘"}</div>