refactor: 页眉由 App 统一注入（ScreenLayout），三页共用一致页眉

- 新增 ScreenLayout 布局路由：注入共享 PageHeader + 全局左右键循环导航
- PageHeader 无 props，按路由自动识别状态（数据实时/3D 实时/媒体播放）
- DataScreen / DigitalTwin / MediaScreen 移除各自页眉，避免重复
- 页脚按页面按需保留（数据大屏 + 媒体轮播，数字孪生无）
- 管理后台不参与导航循环；旧 /screen2 路由移除
- 补齐 MediaScreen 音量/播放/翻页图标与浅色主题样式

src/components/Icons.jsx

@@ -9,6 +9,7 @@ import {
   Check, Gauge, Cpu, Server, Database, Sparkles, Bulb, Settings,
   Heart, Pill, Dna, Microscope, Atom, MapPin, Flag, Award, Medal,
   History, Drone, Plane, Rocket, Satellite, Wallet, UserPlus, Activity,
+  Volume, VolumeOff, ChevronLeft, ChevronRight, PlayerPlay, PlayerPause,
 } from '@appica/icons-react';
 
 /* 名称 → 图标组件映射（推荐的调用方式：icon="bolt"） */
@@ -64,6 +65,14 @@ const NAME_MAP = {
   wallet: Wallet,
   'user-plus': UserPlus,
   activity: Activity,
+  volume: Volume,
+  'volume-off': VolumeOff,
+  'chevron-left': ChevronLeft,
+  'chevron-right': ChevronRight,
+  'player-play': PlayerPlay,
+  'player-pause': PlayerPause,
+  play: PlayerPlay,
+  pause: PlayerPause,
 };
 
 /**
@@ -95,4 +104,5 @@ export {
   Check, Gauge, Cpu, Server, Database, Sparkles, Bulb, Settings,
   Heart, Pill, Dna, Microscope, Atom, MapPin, Flag, Award, Medal,
   History, Drone, Plane, Rocket, Satellite, Wallet, UserPlus, Activity,
+  Volume, VolumeOff, ChevronLeft, ChevronRight, PlayerPlay, PlayerPause,
 };