Update backend/app/pipeline/turns.py

Fixing ASCII encoding error by forcing UTF-8

backend/app/pipeline/turns.py

@@ -11,7 +11,7 @@ def fmt_time(seconds: float) -> str:
 def load_turns(transcript_json: Path, speaker_map: dict[str, str] | None = None) -> list[dict]:
     """Parse whisperx json into merged (start, end, speaker, text) turns.
     speaker_map maps raw labels (SPEAKER_00...) to display names; unmapped labels pass through raw."""
-    data = json.loads(transcript_json.read_text())
+    data = json.loads(transcript_json.read_text(encoding="utf-8"))
     speaker_map = speaker_map or {}
     turns = []
     for seg in data.get("segments", []):