fix: prevent double-counting of sleep sessions in stats by grouping by start date

backend/app/crud.py

@@ -113,22 +113,27 @@ async def update_session(
     return sleep_session
 
 
-async def get_all_time_stats(session: AsyncSession) -> tuple[int, float]:
-    statement = select(func.count(), func.min(SleepSession.start_time))
+async def get_sleep_counts_by_start_date(
+    session: AsyncSession,
+    from_date: Optional[datetime] = None,
+    to_date: Optional[datetime] = None,
+) -> List[tuple]:
+    if to_date and to_date.hour == 0 and to_date.minute == 0 and to_date.second == 0 and to_date.microsecond == 0:
+        to_date = to_date.replace(hour=23, minute=59, second=59, microsecond=999999)
+
+    query_to_date = to_date.replace(tzinfo=None) if to_date and to_date.tzinfo else to_date
+    query_from_date = from_date.replace(tzinfo=None) if from_date and from_date.tzinfo else from_date
+
+    statement = (
+        select(func.date(SleepSession.start_time), func.count())
+        .group_by(func.date(SleepSession.start_time))
+        .order_by(func.date(SleepSession.start_time).desc())
+    )
+
+    if query_from_date:
+        statement = statement.where(SleepSession.start_time >= query_from_date)
+    if query_to_date:
+        statement = statement.where(SleepSession.start_time <= query_to_date)
+
     result = await session.exec(statement)
-    total_sessions, first_session_time = result.one()
-
-    if total_sessions == 0 or first_session_time is None:
-        return 0, 0.0
-
-    # DB has naive datetimes
-    first_session_time_naive = first_session_time.replace(tzinfo=None)
-    
-    # Get current date (naive for comparison)
-    today_date = datetime.now().date()
-    first_date = first_session_time_naive.date()
-    
-    num_days = (today_date - first_date).days + 1
-    avg_sleeps = total_sessions / num_days if num_days > 0 else 0.0
-    
-    return total_sessions, avg_sleeps
+    return list(result.all())