refactor(client): 裸色字面量 F0F6FF/F0F4FF 迁移到 token

入库选填区/退单提示条 F0F6FF → infoSoft；表格列头 F0F4FF → thBg；
登录历史项/外壳用户菜单 hover → rowHover、菜单文字 → text。
深色主题 B / 暖色主题 C 下这些 chrome 现可正确随主题换色。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TSKEiHsvauyxYUW2itzUXX

client/lib/screens/shell/app_shell.dart

@@ -1012,8 +1012,8 @@ class _HoverMenuItemState extends State<_HoverMenuItem> {
 
   @override
   Widget build(BuildContext context) {
-    const color = Color(0xFF333333);
-    const hoverBg = Color(0xFFF0F4FF);
+    final color = context.tokens.text;
+    final hoverBg = context.tokens.rowHover;
 
     return MouseRegion(
       onEnter: (_) => setState(() => _hovered = true),