make streaks and the leaderboard live, and stop three AI chats from freezing the API

Found in a deeper pass over what the frontend's flow actually touches:

- Nothing in the app ever wrote StreakRecord: "days in a row" was 0 forever
  for every real user. Answers and lesson/island completions now record the
  day (Tehran time); a broken chain shows 0. A streak error never fails the
  answer itself.
- /api/leaderboard only changed when someone ran rebuild_leaderboard by
  hand. It is now computed live (60s cache); weekly counts island XP too.
- gunicorn ran 3 sync workers with a 30s timeout, so every "ask Pi" stream
  pinned a whole worker (~10s, GapGPT buffers the answer) and three at once
  queued the entire API. gunicorn.conf.py (read automatically from the
  working directory) switches to gthread, 8 threads, 120s timeout.
- Every /api/ response now says Cache-Control: private, no-store, so turning
  on caching in the ArvanCloud panel can never serve one student another's data.
- /api/user/summary named no active plan ever ("subscription app not
  implemented yet" had long stopped being true).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

content/views.py

@@ -1,3 +1,5 @@
+import logging
+
 from django.core.cache import cache
 from django.db import IntegrityError, transaction
 from django.db.models import Count, F
@@ -43,6 +45,8 @@ from .serializers import (
     QuestionReportResponseSerializer,
 )
 
+logger = logging.getLogger(__name__)
+
 
 class GuestAwareContentThrottle(ScopedRateThrottle):
     """
@@ -163,6 +167,18 @@ class GradesListView(APIView):
         return Response(GradesListResponseSerializer(_grades_payload()).data)
 
 
+def _record_streak(user_id):
+    """
+    فعالیتِ امروز را در استریک ثبت می‌کند. خطایش هرگز نباید ثبتِ پاسخ یا
+    تمام شدنِ درس را خراب کند — استریک تزئینی است، پیشرفت نیست.
+    """
+    try:
+        from progress.services import record_activity
+        record_activity(user_id)
+    except Exception:  # noqa: BLE001
+        logger.exception('streak: ثبتِ فعالیتِ کاربر %s شکست خورد', user_id)
+
+
 def _node_status(lesson_ids, completed_ids, is_first_unlocked_candidate, quiz_completed=False):
     # آزمونِ مبحث تمام شده → مبحث تمام است، مستقل از تک‌تکِ درس‌ها.
     if quiz_completed:
@@ -437,6 +453,7 @@ class QuestionAnswerView(APIView):
             'heartsRemaining': hearts_remaining if hearts_remaining is not None else 5,
             'mascotMood': 'happy' if choice.is_correct else 'encourage',
         }
+        _record_streak(user_id)
         return Response(AnswerResponseSerializer(data).data)
 
 
@@ -593,6 +610,7 @@ class LessonCompleteView(APIView):
             'coinsEarned': coins_earned,
             'stats': stats_payload,
         }
+        _record_streak(user_id)
         return Response(LessonCompleteResponseSerializer(data).data)
 
 
@@ -904,6 +922,7 @@ class NodeQuizCompleteView(APIView):
                 raise
             stats = UserStats.objects.filter(user_id=user_id).first()
 
+        _record_streak(user_id)
         return respond(completion, stats)