fix: solucionar bug de comparacion de fechas offset-naive y offset-aware en las politicas de retencion

backend/app/services/retention_service.py

@@ -35,11 +35,17 @@ async def apply_retention_policy(db: AsyncSession, job_id: int) -> int:
     # Always keep the most recent backup regardless of age to avoid empty repo
     protected_file_ids.add(backup_files[0].id)
 
+    def ensure_utc(dt: datetime) -> datetime:
+        if dt.tzinfo is None:
+            return dt.replace(tzinfo=timezone.utc)
+        return dt.astimezone(timezone.utc)
+
     # 1. Daily retention: Keep 1 backup per calendar day for the last `job.keep_daily` days
     seen_days = set()
     for bf in backup_files:
-        day_key = bf.created_at.strftime("%Y-%m-%d")
+        bf_created = ensure_utc(bf.created_at)
-        age_days = (now - bf.created_at).total_seconds() / 86400.0
+        day_key = bf_created.strftime("%Y-%m-%d")
+        age_days = (now - bf_created).total_seconds() / 86400.0
         if age_days <= job.keep_daily:
             if day_key not in seen_days:
                 seen_days.add(day_key)
@@ -48,8 +54,9 @@ async def apply_retention_policy(db: AsyncSession, job_id: int) -> int:
     # 2. Weekly retention: Keep 1 backup per calendar week for the last `job.keep_weekly` weeks
     seen_weeks = set()
     for bf in backup_files:
-        week_key = f"{bf.created_at.year}-W{bf.created_at.isocalendar()[1]:02d}"
+        bf_created = ensure_utc(bf.created_at)
-        age_weeks = (now - bf.created_at).total_seconds() / (86400.0 * 7)
+        week_key = f"{bf_created.year}-W{bf_created.isocalendar()[1]:02d}"
+        age_weeks = (now - bf_created).total_seconds() / (86400.0 * 7)
         if age_weeks <= job.keep_weekly:
             if week_key not in seen_weeks:
                 seen_weeks.add(week_key)
@@ -58,9 +65,10 @@ async def apply_retention_policy(db: AsyncSession, job_id: int) -> int:
     # 3. Monthly retention: Keep 1 backup per calendar month for the last `job.keep_monthly` months
     seen_months = set()
     for bf in backup_files:
-        month_key = bf.created_at.strftime("%Y-%m")
+        bf_created = ensure_utc(bf.created_at)
+        month_key = bf_created.strftime("%Y-%m")
         # Approximate age in months (30 days per month)
-        age_months = (now - bf.created_at).total_seconds() / (86400.0 * 30.4375)
+        age_months = (now - bf_created).total_seconds() / (86400.0 * 30.4375)
         if age_months <= job.keep_monthly:
             if month_key not in seen_months:
                 seen_months.add(month_key)