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/components/PasteModal.vue

@@ -69,24 +69,24 @@ async function typeChar(char: string, signal: AbortSignal): Promise<boolean> {
     return true
   }
 
-  const { keyCode, shift } = mapping
-  const modifiers = shift ? { shift: true } : undefined
+  const { hidCode, shift } = mapping
+  const modifier = shift ? 0x02 : 0
 
   try {
     // Send keydown
-    await hidApi.keyboard('down', keyCode, modifiers)
+    await hidApi.keyboard('down', hidCode, modifier)
 
     // Small delay between down and up to ensure key is registered
     await sleep(5)
 
     if (signal.aborted) {
       // Even if aborted, still send keyup to release the key
-      await hidApi.keyboard('up', keyCode, modifiers)
+      await hidApi.keyboard('up', hidCode, modifier)
       return false
     }
 
     // Send keyup
-    await hidApi.keyboard('up', keyCode, modifiers)
+    await hidApi.keyboard('up', hidCode, modifier)
 
     // Additional small delay after keyup to ensure it's processed
     await sleep(2)
@@ -96,7 +96,7 @@ async function typeChar(char: string, signal: AbortSignal): Promise<boolean> {
     console.error('[Paste] Failed to type character:', char, error)
     // Try to release the key even on error
     try {
-      await hidApi.keyboard('up', keyCode, modifiers)
+      await hidApi.keyboard('up', hidCode, modifier)
     } catch {
       // Ignore cleanup errors
     }