移除 scan-topbar-logo 品牌标记

- 从 ScanTerminalDashboard.tsx 移除 logo div 和 brand 容器
- 从 ScanTerminalShell.module.css 移除 .scan-topbar-brand / .scan-topbar-logo 样式
- 从 ScanTerminalLightTheme.module.css 移除对应的浅色主题覆盖

frontend/components/dashboard/ScanTerminalDashboard.tsx

@@ -399,9 +399,7 @@ function ScanTerminalScreen() {
       >
         <main className="scan-data-grid">
           <div className="scan-topbar">
-            <div className="scan-topbar-brand">
-              <div className="scan-topbar-logo" aria-hidden="true" />
-              <div className="scan-topbar-title">
+            <div className="scan-topbar-title">
                 <strong>{isEn ? "AI Weather Decision Terminal" : "AI 天气交易决策台"}</strong>
               <span>
                 {isEn
@@ -409,7 +407,6 @@ function ScanTerminalScreen() {
                   : "从地图选城市，再打开决策卡验证天气证据"}
               </span>
             </div>
-            </div>
             <div className="scan-topbar-actions">
               <button
                 type="button"