fix: 暗色主题全面优化 - 滚动条、颜色适配、dark:伪类修复

- 添加全局暗色滚动条样式 (globals.css)
- 修复 channels/subscriptions 页面 dark: 伪类无效的bug (改用 isDark)
- 修复 RefundDialog 暗色下退款金额、disabled 按钮颜色
- 修复 admin OrderTable 暗色下缺少背景色
- 统一所有 admin 页面 text-gray-500 为 slate 色系
- 修复 UserSubscriptions 续费按钮暗色适配
- 修复日期标签文字缺少暗色颜色类
- MainTabs 暗色容器改用 slate-900 提升对比度
- OpenAI 默认模型区域暗色边框透明度提升
- 更新 README 文档

src/components/admin/OrderTable.tsx

@@ -85,7 +85,7 @@ export default function OrderTable({ orders, onRetry, onCancel, onViewDetail, da
             <th className={thCls}>{text.actions}</th>
           </tr>
         </thead>
-        <tbody className={`divide-y ${dark ? 'divide-slate-700/60' : 'divide-gray-200 bg-white'}`}>
+        <tbody className={`divide-y ${dark ? 'divide-slate-700/60 bg-slate-900' : 'divide-gray-200 bg-white'}`}>
           {orders.map((order) => {
             const statusInfo = {
               label: formatStatus(order.status, locale),
@@ -128,12 +128,12 @@ export default function OrderTable({ orders, onRetry, onCancel, onViewDetail, da
                     {order.id.slice(0, 12)}...
                   </button>
                 </td>
-                <td className={`whitespace-nowrap px-4 py-3 text-sm ${dark ? 'text-slate-200' : ''}`}>
+                <td className={`whitespace-nowrap px-4 py-3 text-sm ${dark ? 'text-slate-200' : 'text-slate-900'}`}>
                   {order.userName || `#${order.userId}`}
                 </td>
                 <td className={tdMuted}>{order.userEmail || '-'}</td>
                 <td className={tdMuted}>{order.userNotes || '-'}</td>
-                <td className={`whitespace-nowrap px-4 py-3 text-sm font-medium ${dark ? 'text-slate-200' : ''}`}>
+                <td className={`whitespace-nowrap px-4 py-3 text-sm font-medium ${dark ? 'text-slate-200' : 'text-slate-900'}`}>
                   {currency}
                   {order.amount.toFixed(2)}
                 </td>

src/components/admin/RefundDialog.tsx

@@ -81,12 +81,12 @@ export default function RefundDialog({
         <div className="mt-4 space-y-3">
           <div className={['rounded-lg p-3', dark ? 'bg-slate-800' : 'bg-gray-50'].join(' ')}>
             <div className={['text-sm', dark ? 'text-slate-400' : 'text-gray-500'].join(' ')}>{text.orderId}</div>
-            <div className="text-sm font-mono">{orderId}</div>
+            <div className={['text-sm font-mono', dark ? 'text-slate-200' : 'text-gray-900'].join(' ')}>{orderId}</div>
           </div>
 
           <div className={['rounded-lg p-3', dark ? 'bg-slate-800' : 'bg-gray-50'].join(' ')}>
             <div className={['text-sm', dark ? 'text-slate-400' : 'text-gray-500'].join(' ')}>{text.amount}</div>
-            <div className="text-lg font-bold text-red-600">
+            <div className={['text-lg font-bold', dark ? 'text-red-400' : 'text-red-600'].join(' ')}>
               {currency}
               {amount.toFixed(2)}
             </div>
@@ -127,7 +127,7 @@ export default function RefundDialog({
                 onChange={(e) => setForce(e.target.checked)}
                 className={['rounded', dark ? 'border-slate-600' : 'border-gray-300'].join(' ')}
               />
-              <span className="text-red-600">{text.forceRefund}</span>
+              <span className={dark ? 'text-red-400' : 'text-red-600'}>{text.forceRefund}</span>
             </label>
           )}
         </div>
@@ -147,7 +147,10 @@ export default function RefundDialog({
           <button
             onClick={handleConfirm}
             disabled={loading || (requireForce && !force)}
-            className="flex-1 rounded-lg bg-red-600 py-2 text-sm font-medium text-white hover:bg-red-700 disabled:cursor-not-allowed disabled:bg-gray-300"
+            className={[
+              'flex-1 rounded-lg py-2 text-sm font-medium text-white hover:bg-red-700 disabled:cursor-not-allowed',
+              dark ? 'bg-red-600/90 disabled:bg-slate-700 disabled:text-slate-500' : 'bg-red-600 disabled:bg-gray-300 disabled:text-gray-400',
+            ].join(' ')}
           >
             {loading ? text.processing : text.confirm}
           </button>