Fix daily email timing to work across all timezones

Critical fix: Task now runs every hour instead of once at 6 AM UTC.
This ensures users in all timezones receive their email at 6 AM local time.

Changes:
- Run task every hour instead of once daily
- Check if it's 6-7 AM in user's timezone (1 hour window)
- Track sent emails in Notification model to prevent duplicates
- Add 'daily_email' notification type

Without this fix, users in timezones where 6 AM UTC is not morning
would never receive their daily email.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

notifications/tasks.py

@@ -45,13 +45,25 @@ def send_daily_task_email():
         user_local_time = timezone.now().astimezone(user_tz)
         user_local_hour = user_local_time.hour
 
-        # Only send if it's between 6-9 AM in the user's timezone
-        if not (6 <= user_local_hour < 9):
+        # Only send if it's between 6-7 AM in the user's timezone
+        # (gives 1 hour window, task runs every hour)
+        if not (6 <= user_local_hour < 7):
             continue
 
         # Get today's date in user's timezone
         today = user_local_time.date()
 
+        # Check if we already sent an email today
+        from .models import Notification
+        already_sent_today = Notification.objects.filter(
+            user=user,
+            notification_type='daily_email',
+            created_at__date=today
+        ).exists()
+
+        if already_sent_today:
+            continue
+
         # Get tasks due today
         tasks_due_today = Task.objects.filter(
             user=user,
@@ -107,6 +119,15 @@ def send_daily_task_email():
                 recipient_list=[user.email],
                 fail_silently=False,
             )
+
+            # Record that we sent the email (prevents duplicates)
+            Notification.objects.create(
+                user=user,
+                notification_type='daily_email',
+                title=subject,
+                message=f"Daily email sent with {tasks_due_today.count()} tasks due today and {overdue_tasks.count()} overdue tasks"
+            )
+
             emails_sent += 1
             logger.info(f"Sent daily task email to {user.email}")
         except Exception as e: