品牌化重构: StreamCore + 现代UI主题 + 英文界面

- 移除所有emoji (HomePage中的🎬改为VideoCameraOutlined图标)
- 主题重设计: 深蓝色系主色(#1E3A5F),系统sans-serif字体
  白色/浅灰背景,现代卡片阴影和圆角,完全去除复古感
- 首页移除管理入口,纯观众视角(渐变横幅+卡片列表)
- 统一品牌名称 StreamCore (替换LiveStream)
- 全部界面英文(antd默认locale,去除zhCN)
- 登录页渐变+卡片居中布局

frontend/src/admin/pages/Dashboard.tsx

@@ -1,9 +1,9 @@
 import { useState, useEffect } from 'react'
 import { Row, Col, Card, Statistic, Typography, Table, Tag, Space } from 'antd'
-import { VideoCameraOutlined, EyeOutlined, SignalFilled } from '@ant-design/icons'
+import { VideoCameraOutlined, SignalFilled, PlayCircleOutlined } from '@ant-design/icons'
 import { fetchStreams, type StreamInfo } from '../../api/streams'
 
-const { Title } = Typography
+const { Title, Text } = Typography
 
 export default function Dashboard() {
   const [streams, setStreams] = useState<StreamInfo[]>([])
@@ -27,60 +27,65 @@ export default function Dashboard() {
   const pendingCount = streams.filter((s) => s.status === 'pending').length
 
   const statusMap: Record<string, { color: string; label: string }> = {
-    pending: { color: 'blue', label: '待开播' },
-    live: { color: 'green', label: '直播中' },
-    ended: { color: 'default', label: '已结束' },
-    cancelled: { color: 'red', label: '已取消' },
+    pending: { color: 'blue', label: 'Scheduled' },
+    live: { color: 'green', label: 'Live' },
+    ended: { color: 'default', label: 'Ended' },
+    cancelled: { color: 'red', label: 'Cancelled' },
   }
 
   const recentColumns = [
-    { title: '标题', dataIndex: 'title', key: 'title', ellipsis: true },
+    { title: 'Title', dataIndex: 'title', key: 'title', ellipsis: true },
     {
-      title: '状态', dataIndex: 'status', key: 'status',
+      title: 'Status', dataIndex: 'status', key: 'status',
       render: (status: string) => {
         const s = statusMap[status] || { color: 'default', label: status }
         return <Tag color={s.color}>{s.label}</Tag>
       },
+      width: 110,
+    },
+    {
+      title: 'Created', dataIndex: 'created_at', key: 'created_at',
+      render: (v: string) => v?.slice(0, 16),
+      width: 170,
     },
-    { title: '创建时间', dataIndex: 'created_at', key: 'created_at', render: (v: string) => v?.slice(0, 16) },
   ]
 
   return (
     <div>
-      <Title level={3} style={{ marginBottom: 24 }}>概览</Title>
+      <Title level={3} style={{ marginBottom: 24, fontWeight: 600 }}>Overview</Title>
       <Row gutter={[24, 24]}>
         <Col xs={24} sm={8}>
-          <Card>
+          <Card style={{ borderRadius: 12 }}>
             <Statistic
-              title="直播中"
+              title="Live Now"
               value={liveCount}
-              prefix={<SignalFilled style={{ color: '#52c41a' }} />}
+              prefix={<SignalFilled style={{ color: '#2E7D32' }} />}
               loading={loading}
             />
           </Card>
         </Col>
         <Col xs={24} sm={8}>
-          <Card>
+          <Card style={{ borderRadius: 12 }}>
             <Statistic
-              title="待开播"
+              title="Scheduled"
               value={pendingCount}
-              prefix={<VideoCameraOutlined style={{ color: '#1677ff' }} />}
+              prefix={<VideoCameraOutlined style={{ color: '#1565C0' }} />}
               loading={loading}
             />
           </Card>
         </Col>
         <Col xs={24} sm={8}>
-          <Card>
+          <Card style={{ borderRadius: 12 }}>
             <Statistic
-              title="直播总数"
+              title="Total Streams"
               value={streams.length}
-              prefix={<EyeOutlined />}
+              prefix={<PlayCircleOutlined />}
               loading={loading}
             />
           </Card>
         </Col>
       </Row>
-      <Card title="最近直播" style={{ marginTop: 24 }}>
+      <Card title="Recent Streams" style={{ marginTop: 24, borderRadius: 12 }}>
         <Table
           dataSource={streams.slice(0, 10)}
           columns={recentColumns}