🔧 Frontend review fixes & quality improvements

- Fixed race condition in apiCache TTL handling by passing ttl per-entry
- Removed double snapshot reassignment bug after switch cases in useRenderers.ts  
- Replaced `as any` cast on transport_state with runtime guard (isTransportState)
- Fixed invalidate() to preserve subscriptions instead of deleting them
- Migrated reactive(Map) → shallowRef + explicit reactivity triggers (triggerSnapshotReactive, triggerLoadingReactice)
- Added onUnmounted cleanup for debounce timer in useRenderer()
- Exposed resetSSE() to allow reinitialization after SSE reconnect
- Split deep watch in useTabs.ts into separate lightweight watches without {deep: true}
- Fixed swipe gesture to capture startX in onSwipeStart instead of using final clientX
- Added minimal JSON validation log for null responses (DEV mode only)
- Implemented ARIA labels on transport controls and volume slider
- Added UI notifications for network errors via uiStore.notifyError()
+ Removed obsolete toRaw() usage and import after shallowRef migration
- Added missing reactivity triggers for state_changed, queue_refreshing/updated cases

pmoapp/webapp/src/components/pmocontrol/VolumeControl.vue

@@ -65,6 +65,7 @@ async function handleToggleMute() {
             class="btn btn-icon"
             @click="handleToggleMute"
             :title="state?.mute ? 'Réactiver le son' : 'Couper le son'"
+            :aria-label="state?.mute ? 'Réactiver le son' : 'Couper le son'"
         >
             <VolumeX v-if="state?.mute" :size="20" />
             <Volume2 v-else :size="20" />
@@ -78,6 +79,7 @@ async function handleToggleMute() {
             @input="handleVolumeChange"
             class="volume-slider"
             :disabled="state?.mute ?? false"
+            aria-label="Volume"
         />
 
         <span class="volume-value">{{ localVolume }}</span>