controller: UI-toggle audio output + astreamselect decouple (Phase 7 Вариант 2)

Web UI checkbox в Audio source карточке: «вывод аудио в стрим». Off →
TV получает silence + downstream audio chain isolated от live-audio RTSP
(нестабильный sidecar поток больше не блокирует video pipeline).

Изменения:
  state.InstanceState: + audio_output_enabled (default True)
  config.InstanceCfg:
    + audio_output_volume_target (default volume@output_audio)
    + audio_input_select_target (default astreamselect@audio_input)
  dispatch.set_audio_output_enabled(enabled):
    enabled=False → astreamselect map=1 (anullsrc) + volume=0
    enabled=True  → astreamselect map=0 (live-audio) + volume=1
    Двойная команда: select decouples upstream, volume гарантирует тишину
    на случай если в anullsrc что-то не так.
  http_api: + GET /audio-output/{instance}, POST /audio-output/{instance}
  static/index.html: + checkbox в Audio source header + loadAudioOut/toggleAudioOut

ZMQ smoke test OK. HTTP roundtrip OK.

Сопутствующий pipeline change: docker-compose.phase7.yml — amix заменён
на astreamselect@audio_input (см. localhost-infra commit).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

controller/cuda_grid_controller/http_api.py

@@ -34,6 +34,10 @@ class AutoLayoutReq(BaseModel):
     enabled: bool
 
 
+class AudioOutputReq(BaseModel):
+    enabled: bool
+
+
 def create_app(
     cfg: Config, state: ControllerState, dispatcher: CommandDispatcher,
     snapshot_history: SnapshotHistory | None = None,
@@ -80,6 +84,22 @@ def create_app(
             }
         return {"instances": out}
 
+    @app.get("/audio-output/{instance}")
+    async def audio_output_get(instance: str) -> dict[str, Any]:
+        _check_instance(instance)
+        return {
+            "instance": instance,
+            "enabled": await state.get_audio_output_enabled(instance),
+        }
+
+    @app.post("/audio-output/{instance}")
+    async def audio_output_set(instance: str, req: AudioOutputReq) -> dict[str, Any]:
+        _check_instance(instance)
+        ok = await dispatcher.set_audio_output_enabled(instance, req.enabled)
+        if not ok:
+            raise HTTPException(500, "audio output ZMQ command failed (см. logs)")
+        return {"ok": True, "instance": instance, "enabled": req.enabled}
+
     @app.post("/layout/{instance}/set")
     async def set_layout(instance: str, req: LayoutSetReq) -> dict[str, Any]:
         _check_instance(instance)