fix: 优化 WebRTC 建连流程、修复平台信息、修复虚拟键盘键值映射

- WebRTC：默认 mDNS 调整为 QueryOnly，Answer 阶段改为等待 ICE gathering complete（2.5s 超时），提升首次建连成功率与候选完整性
- WebRTC：前端建连流程增加阶段化状态与串行保护（connectInFlight/ready gate），优化配置变更后的重连时机与失败处理，减少竞态和无效重试
- Device：平台信息补充 `/proc/device-tree/model` 回退并统一展示为“处理器/平台”
- HID：键盘输入链路统一为 HID usage + modifier bitmask，修复虚拟键盘/宏/粘贴键值映射错误

web/src/i18n/en-US.ts

@@ -312,6 +312,14 @@ export default {
     webrtcConnectedDesc: 'Using low-latency H.264 video stream',
     webrtcFailed: 'WebRTC Connection Failed',
     fallingBackToMjpeg: 'Falling back to MJPEG mode',
+    webrtcPhaseIceServers: 'Loading ICE servers...',
+    webrtcPhaseCreatePeer: 'Creating peer connection...',
+    webrtcPhaseCreateChannel: 'Creating data channel...',
+    webrtcPhaseCreateOffer: 'Creating local offer...',
+    webrtcPhaseWaitAnswer: 'Waiting for remote answer...',
+    webrtcPhaseSetRemote: 'Applying remote description...',
+    webrtcPhaseApplyIce: 'Applying ICE candidates...',
+    webrtcPhaseNegotiating: 'Negotiating secure connection...',
     // Pointer Lock
     pointerLocked: 'Pointer Locked',
     pointerLockedDesc: 'Press Escape to release the pointer',
@@ -455,7 +463,7 @@ export default {
     deviceInfo: 'Device Info',
     deviceInfoDesc: 'Host system information',
     hostname: 'Hostname',
-    cpuModel: 'CPU Model',
+    cpuModel: 'Processor / Platform',
     cpuUsage: 'CPU Usage',
     memoryUsage: 'Memory Usage',
     networkAddresses: 'Network Addresses',