fix: sleep quality calculation using wrong key (stage vs phase)

BUG: sleep_avg_quality showed 0% despite valid sleep data
ROOT CAUSE: sleep_segments use 'phase' key, not 'stage'
FIX: Changed s.get('stage') to s.get('phase') in get_sleep_avg_quality()

version: 9.5.1 (bugfix)
module: prompts 2.0.1

backend/placeholder_resolver.py

@@ -347,8 +347,8 @@ def get_sleep_avg_quality(profile_id: str, days: int = 7) -> str:
         for row in rows:
             segments = row['sleep_segments']
             if segments:
-                # Note: stages are stored lowercase (deep, rem, light, awake)
-                deep_rem_min = sum(s.get('duration_min', 0) for s in segments if s.get('stage') in ['deep', 'rem'])
+                # Note: segments use 'phase' key (not 'stage'), stored lowercase (deep, rem, light, awake)
+                deep_rem_min = sum(s.get('duration_min', 0) for s in segments if s.get('phase') in ['deep', 'rem'])
                 total_min = sum(s.get('duration_min', 0) for s in segments)
                 if total_min > 0:
                     quality_pct = (deep_rem_min / total_min) * 100