feat: dashboard UI + key API + realtime decode

Full HTML dashboard (dark theme, vanilla JS, no external deps) served at / and /dashboard with five tabs: system status (admin), file upload-to-transcribe with progress/result/downloads, job history with cancel/result modal, realtime mic demo over the existing WebSocket, and API key create/list.

Backend: POST/GET /v1/keys (admin; raw key returned once, digest-only storage); KeyStore.list_keys(); EngineOwner.emit_hypothesis is now a real implementation (PCM16 chunk -> WAV -> realtime-lane decode with the single GPU lock) instead of a stub.

Notebook: tunnel cell links /dashboard and smoke-checks the HTML.

+ 6 tests (dashboard public HTML, key create/list/scope, WAV header, emit_hypothesis cleanup). 153 tests pass, ruff clean, JS syntax verified with node --check.

tests/unit/test_engine_owner.py

@@ -34,6 +34,74 @@ def _opts(**kw) -> TranscriptionOptions:
     return TranscriptionOptions(**kw)
 
 
+class _SegFakeEngine:
+    """emit_hypothesis 테스트용 — WAV 경로 기록 + 세그먼트 반환."""
+
+    def __init__(self) -> None:
+        self.path = None
+
+    def transcribe(self, audio_path, options, should_cancel=None, download_progress=None):
+        self.path = audio_path
+        segs = [
+            {
+                "start": 0.0,
+                "end": 1.2,
+                "text": "안녕하세요",
+                "avg_logprob": -0.2,
+                "no_speech_prob": 0.01,
+            }
+        ]
+        return type("O", (), {"segments": iter(segs), "info": {"language": "ko"}})()
+
+    def unload_all(self):
+        pass
+
+
+def _bare_owner(engine) -> EngineOwner:
+    import threading
+
+    from luke_scribe.config import Settings
+
+    owner = EngineOwner.__new__(EngineOwner)
+    owner.settings = Settings(_env_file=None)
+    owner._engine = engine
+    owner._lock = threading.Lock()
+    owner._realtime_priority = threading.Lock()
+    owner._stats = {"jobs": 0, "downgrades": 0, "oom": 0}
+    return owner
+
+
+def test_pcm16_to_wav_header():
+    import struct
+
+    from luke_scribe.engine.owner import _pcm16_to_wav
+
+    wav = _pcm16_to_wav(b"\x00\x00" * 8000)  # 1초 (16kHz mono)
+    assert wav[:4] == b"RIFF"
+    assert wav[8:12] == b"WAVE"
+    assert wav[12:16] == b"fmt "
+    sr = struct.unpack("<I", wav[24:28])[0]
+    channels = struct.unpack("<H", wav[22:24])[0]
+    bits = struct.unpack("<H", wav[34:36])[0]
+    assert sr == 16000 and channels == 1 and bits == 16
+    assert struct.unpack("<I", wav[40:44])[0] == 16000  # data 크기
+
+
+def test_emit_hypothesis_decodes_chunk_and_cleans_temp():
+    import os
+
+    engine = _SegFakeEngine()
+    owner = _bare_owner(engine)
+    chunk = b"\x00\x00" * 16000  # 1초 PCM16
+    out = owner.emit_hypothesis(chunk)
+    assert out["audio_sec"] == 1.0
+    assert len(out["segments"]) == 1
+    assert out["segments"][0].model_dump()["text"] == "안녕하세요"
+    # 임시 WAV는 실시간 레인 decode 후 삭제됨
+    assert engine.path is not None
+    assert not os.path.exists(engine.path)
+
+
 def test_no_downgrade_on_success():
     owner = EngineOwner.__new__(EngineOwner)
     owner.settings = None