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/users/tests/integration/test_auth_flows.py

@@ -0,0 +1,48 @@
+import pytest
+
+from apps.users.models import User, UserSocialAccount
+from apps.users.services import auth
+from apps.users.services import google_oauth as google
+
+
+pytestmark = [pytest.mark.integration, pytest.mark.django_db]
+
+
+def test_registration_consumes_verified_mobile_and_creates_account(fake_redis, monkeypatch):
+    monkeypatch.setattr(auth, "_redis", lambda: fake_redis)
+    fake_redis.set(auth._verified_otp_key("register", "09190000001"), "1")
+    payload = auth.RegistrationPayload(
+        username="new_member", mobile="09190000001", password="StrongPass123!", code="12345",
+        email=" NEW@EXAMPLE.COM ",
+    )
+    user = auth.register_user(payload)
+    assert user.email == "new@example.com"
+    assert user.is_mobile_verified
+    assert user.check_password("StrongPass123!")
+    assert fake_redis.get(auth._verified_otp_key("register", "09190000001")) is None
+
+
+def test_registration_rejects_duplicate_username(user_factory, fake_redis, monkeypatch):
+    user_factory(username="taken")
+    monkeypatch.setattr(auth, "_redis", lambda: fake_redis)
+    payload = auth.RegistrationPayload(username="taken", mobile="09190000002", password="StrongPass123!", code="12345")
+    with pytest.raises(auth.AuthServiceError) as error:
+        auth.register_user(payload)
+    assert error.value.field == "username"
+    assert User.objects.count() == 1
+
+
+def test_google_claim_creates_account_and_link_without_live_gateway(mocker):
+    verify = mocker.patch("apps.users.services.google_oauth.verify_otp_code")
+    profile = google.GoogleProfile("google-1", "person@example.com", True, "Person", "Example", "")
+    flow = google.create_google_flow({
+        "status": "claim_required", "resolution": "new_account", "mobile": "09190000001",
+        "username": "google_member", "google_profile": google._profile_payload(profile),
+    })
+    result = google.verify_google_claim(flow, "12345")
+    assert result["status"] == "authenticated"
+    verify.assert_called_once()
+    user = User.objects.get(username="google_member")
+    assert user.is_mobile_verified
+    assert not user.has_usable_password()
+    assert UserSocialAccount.objects.filter(user=user, provider_user_id="google-1").exists()