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/auth/login_screen.dart

@@ -714,7 +714,7 @@ class _HistoryMenuItemState extends State<_HistoryMenuItem> {
       onExit: (_) => setState(() => _hovered = false),
       cursor: SystemMouseCursors.click,
       child: Material(
-        color: _hovered ? const Color(0xFFF0F4FF) : Colors.white,
+        color: _hovered ? context.tokens.rowHover : context.tokens.surface,
         child: InkWell(
           onTap: widget.onSelected,
           child: Padding(