feat: UAC USB microphone passthrough

- Add UAC1 gadget function (ConfigFS) with optimized endpoint config
- Browser mic capture with Opus encoding via WebCodecs AudioEncoder
- WebSocket audio transport (Opus 64kbps, 100x bandwidth reduction vs raw PCM)
- aplay subprocess for reliable PCM playback to USB gadget
- Settings toggle + ActionBar mic button (hidden when UAC disabled)
- Dynamic PCM device resolution (/proc/asound)
- c_chmask=0 + req_number=4 fixes DWC3 composite isochronous endpoint issue

web/src/components/ActionBar.vue

@@ -3,6 +3,7 @@ import { ref, computed, onMounted, onUnmounted, watch, nextTick } from 'vue'
 import { useI18n } from 'vue-i18n'
 import { useRouter } from 'vue-router'
 import { useSystemStore } from '@/stores/system'
+import { getMicrophone } from '@/composables/useMicrophone'
 import { Button } from '@/components/ui/button'
 import { ButtonGroup } from '@/components/ui/button-group'
 import {
@@ -31,6 +32,7 @@ import {
 } from '@/components/ui/sheet'
 import {
   ClipboardPaste,
+  Mic,
   HardDrive,
   Keyboard,
   Settings,
@@ -68,9 +70,13 @@ const props = defineProps<{
   showTerminal?: boolean
   showComputerUse?: boolean
   showPasteText?: boolean
+  showMic?: boolean
 }>()
 const showStats = computed(() => (props.videoMode ?? 'mjpeg') !== 'mjpeg')
 const showPasteText = computed(() => props.showPasteText !== false)
+const showMic = computed(() => props.showMic === true)
+const mic = getMicrophone()
+
 
 const emit = defineEmits<{
   (e: 'toggleFullscreen'): void
@@ -350,6 +356,24 @@ const hasRightOverflow = computed(() => {
             </PopoverContent>
           </Popover>
         </div>
+
+        <!-- Mic button -->
+        <div v-if="showMic">
+          <TooltipProvider>
+            <Tooltip>
+              <TooltipTrigger as-child>
+                <Button variant="ghost" size="sm" class="h-8 gap-1.5 text-xs"
+                  :class="mic.active.value ? 'text-destructive' : mic.error.value ? 'text-yellow-500' : ''"
+                  @click="mic.toggle()">
+                  <Mic class="size-4" :class="mic.active.value ? 'animate-pulse' : ''" />
+                  <span>{{ mic.active.value ? '关闭' : '麦克风' }}</span>
+                  <span v-if="mic.error.value" class="text-[10px]">{{ mic.error.value }}</span>
+                </Button>
+              </TooltipTrigger>
+              <TooltipContent>{{ mic.error.value ? mic.error.value : (mic.active.value ? '停止传声' : '开始传声') }}</TooltipContent>
+            </Tooltip>
+          </TooltipProvider>
+        </div>
       </ButtonGroup>
 
       <!-- Right side buttons -->