feat: initial commit of astra local voice agent

Lokaler deutscher Sprachagent für Apple Silicon: Pipecat-Pipeline mit
Nemotron-ASR (MLX), Qwen über natives Ollama /api/chat, und Pocket TTS.
Loopback-only WebRTC-Server mit Origin/Host-Härtung.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVgSHNHdRx3UNTBodFmhRA

tests/test_stt.py

@@ -0,0 +1,28 @@
+from unittest.mock import AsyncMock, patch
+
+import pytest
+from pipecat.processors.frame_processor import FrameDirection
+
+from astra.core import Settings
+from astra.inference import Models
+from astra.services import NemotronSTTService
+
+
+@pytest.mark.asyncio
+async def test_recognition_failure_reaches_pipeline_upstream_and_notifies_browser():
+    models = Models(Settings())
+    notices = []
+    service = NemotronSTTService(models, notices.append)
+    service.push_frame = AsyncMock()
+    try:
+        service.queue.put_nowait(("start", b""))
+        with patch("astra.services.Recognizer", side_effect=RuntimeError("Model failed")):
+            await service._worker()
+        assert service.failed
+        assert notices[0]["type"] == "error"
+        assert "Model failed" in notices[0]["message"]
+        frame, direction = service.push_frame.call_args.args
+        assert frame.fatal
+        assert direction == FrameDirection.UPSTREAM
+    finally:
+        await models.close()