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/widgets/data_table_card.dart

@@ -150,7 +150,7 @@ class _DataTableCardState extends State<DataTableCard> {
 
   TableRow _buildHeaderRow() {
     return TableRow(
-      decoration: const BoxDecoration(color: Color(0xFFF0F4FF)),
+      decoration: BoxDecoration(color: context.tokens.thBg),
       children: widget.columns.map((col) {
         return Padding(
           padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),

client/lib/widgets/order_return_dialog.dart

@@ -270,7 +270,7 @@ class _OrderReturnDialogState extends State<_OrderReturnDialog> {
               margin: const EdgeInsets.fromLTRB(16, 2, 16, 8),
               padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 8),
               decoration: BoxDecoration(
-                color: const Color(0xFFF0F6FF),
+                color: context.tokens.infoSoft,
                 border: Border(left: BorderSide(color: context.tokens.primary, width: 3)),
                 borderRadius: BorderRadius.circular(4),
               ),