test: migrate backend suites to pytest with module coverage gate

Split backend tests into unit and integration suites, add isolated fixtures and coverage enforcement, and update CI and test documentation. Cover current authentication, content, notification, payment, media, and admin flows; fix behaviors revealed by the new tests. Validate both suites and the per-module gate against local PostgreSQL.

apps/events/tests/integration/test_event_models.py

@@ -0,0 +1,35 @@
+import pytest
+from types import SimpleNamespace
+from datetime import timedelta
+from django.contrib import admin
+from django.utils import timezone
+from apps.events.admin import EventAdmin, RegistrationAdmin
+from apps.events.models import Event, Registration
+from apps.events.tasks import send_registration_cancellation_notification, send_registration_confirmation_notification
+from apps.users.models import User
+
+@pytest.mark.django_db
+@pytest.mark.integration
+class TestEventModelTests:
+
+    def setup_method(self):
+        now = timezone.now()
+        self.event = Event.objects.create(title='Workshop', description='**Important** details', start_time=now + timedelta(days=1), end_time=now + timedelta(days=1, hours=2), capacity=1, registration_start_date=now - timedelta(days=1), registration_end_date=now + timedelta(hours=1))
+        self.user = User.objects.create_user(username='attendee', mobile='09191110003', password='password')
+
+    def test_markdown_description_and_registration_window_remain_available(self):
+        assert '<strong>Important</strong>' in self.event.description_html
+        assert self.event.is_registration_open
+        self.event.registration_end_date = timezone.now() - timedelta(minutes=1)
+        assert not self.event.is_registration_open
+
+    def test_capacity_counts_confirmed_registration(self, mocker):
+        delay = mocker.patch('apps.events.tasks.send_registration_confirmation_notification.delay')
+        Registration.objects.create(event=self.event, user=self.user, status=Registration.StatusChoices.CONFIRMED)
+        assert self.event.current_attendees_count == 1
+        assert not self.event.has_available_slots
+        delay.assert_called_once()
+
+    def test_unlimited_capacity_allows_registration(self):
+        self.event.capacity = None
+        assert self.event.has_available_slots