fix heart refill and grant unlimited hearts to active subscribers

next_refill_at was set on UserHearts but never read or recalculated,
so a heart lost to zero never came back. UserHearts.apply_regen() now
catches up missed 24h intervals on read/deduct, and lose_heart() starts
the timer only when it isn't already running.

Any user with an active (non-expired) subscription now skips heart
deduction entirely, regardless of which plan they're on — good enough
for now until per-plan perks are needed.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

subscription/services.py

@@ -1,4 +1,4 @@
-from django.db import transaction
+from django.db import models, transaction
 from django.utils import timezone
 
 from statuslog.signals import status_changed
@@ -6,6 +6,19 @@ from statuslog.signals import status_changed
 from .models import Subscription
 
 
+def has_unlimited_hearts(user_id: int) -> bool:
+    """آیا کاربر اشتراکِ فعال داره (progress.UserHearts از این استفاده می‌کنه تا
+    هارت کم نکنه). فعلاً هر اشتراکِ فعال، فارغ از پلن/مدت، این پرک رو می‌ده —
+    وقتی محصول پلن‌های متفاوت با پرکِ متفاوت خواست، این تابع دقیق‌تر می‌شه.
+    expires_at=None یعنی اشتراکِ نامحدود (grant_free_subscription با duration_days=None)."""
+    now = timezone.now()
+    return Subscription.objects.filter(
+        user_id=user_id, status='active',
+    ).filter(
+        models.Q(expires_at__isnull=True) | models.Q(expires_at__gt=now)
+    ).exists()
+
+
 def activate_subscription(subscription_id: int):
     """
     بعد از تایید پرداخت (payment webhook) صدا زده می‌شود؛ اشتراک را active