fix(web): 项目图标统一用昔涟头像——侧边栏/管理面板顶栏 logo 从旧占位 /icon.svg 改为昔涟

- Nav.tsx(用户端侧边栏)/AdminApp.tsx(管理面板顶栏) 的 <img src="/icon.svg"> 占位 → 昔涟头像(Cyrene-2F-N-Happy-1-192x192.png, 与 favicon/项目图标一致)
- 与角色视觉分离红线: 项目图标/favicon 用昔涟(全局), 聊天头像走 personaAvatar(按角色取, 绝不 fallback 昔涟)
- 修复: 之前定了项目图标用昔涟, 但侧边栏/顶栏仍硬编码旧占位 /icon.svg
- npm run build 绿

frontend/web/src/admin/AdminApp.tsx

@@ -136,7 +136,7 @@ function AdminTopBar({ section, onMenu }: { section: AdminSectionId; onMenu?: ()
         </button>
       ) : null}
       <div className="flex min-w-0 items-center gap-2">
-        <img src="/icon.svg" alt="Cyrene" className="h-7 w-7 shrink-0" />
+        <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" />
         <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>

frontend/web/src/components/Nav.tsx

@@ -68,7 +68,7 @@ function NavContent({ onNavigate }: { onNavigate: () => void }): React.ReactNode
   return (
     <>
       <div className="flex items-center gap-2 px-2 py-2">
-        <img src="/icon.svg" alt="Cyrene" className="h-7 w-7" />
+        <img src="/images/Cyrene_Avatar/2nd_Form/Cyrene-2F-N-Happy-1-192x192.png" alt="Cyrene" className="h-7 w-7 rounded-full object-cover" />
         <div className="leading-tight">
           <div className="text-sm font-semibold">Cyrene</div>
           <div className="text-[11px] text-[var(--mu-text-lo)]">昔涟</div>