G7 증명과 G8 clean-head 승격 준비

apps/api/app/services/session_metrics.py

@@ -3,7 +3,7 @@
 from __future__ import annotations
 
 from dataclasses import dataclass, field
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Any, Callable
 
 from ..store import InProcSession
@@ -44,7 +44,7 @@ class LearnerGrowthMetrics:
 def iso_datetime(ts: float | None) -> str | None:
     if ts is None:
         return None
-    return datetime.fromtimestamp(ts).isoformat(timespec="seconds")
+    return datetime.fromtimestamp(ts, tz=timezone.utc).isoformat(timespec="seconds")
 
 
 def session_activity_time(sess: InProcSession) -> float:

apps/api/app/services/voice.py

@@ -998,7 +998,7 @@ class VoiceService:
             local_whisper_stt_model
             if local_whisper_stt_model is not None
             else settings.local_whisper_stt_model
-        ).strip() or "large-v3"
+        ).strip() or "small"
         self._local_whisper_stt_language = (
             local_whisper_stt_language
             if local_whisper_stt_language is not None