security: fix GoogleLoginView audience check + replace Clerk with direct GIS flow

- verify_oauth2_token now passes GOOGLE_CLIENT_ID as third arg (audience check)
- fail-closed: returns 503 if GOOGLE_CLIENT_ID env var is not set
- add GOOGLE_CLIENT_ID = os.environ.get('GOOGLE_CLIENT_ID', '') to settings
- replace ClerkLoginViewTests with GoogleLoginViewTests (4 cases)
- update requirements-docker.txt

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

mobile_api/tests.py

@@ -1,3 +1,89 @@
-from django.test import TestCase
+"""Unit tests for GoogleLoginView.
 
-# Create your tests here.
+Run with:
+    python manage.py test mobile_api.tests
+"""
+import json
+from unittest.mock import patch, MagicMock
+
+from django.test import TestCase, override_settings
+from rest_framework.authtoken.models import Token
+
+from accounts.models import User
+
+
+@override_settings(GOOGLE_CLIENT_ID='test-client-id.apps.googleusercontent.com')
+class GoogleLoginViewTests(TestCase):
+    url = '/api/user/google-login/'
+
+    def _valid_idinfo(self, email='new.user@example.com'):
+        return {
+            'email': email,
+            'given_name': 'New',
+            'family_name': 'User',
+            'aud': 'test-client-id.apps.googleusercontent.com',
+        }
+
+    @patch('google.oauth2.id_token.verify_oauth2_token')
+    def test_valid_token_creates_user(self, mock_verify):
+        mock_verify.return_value = self._valid_idinfo('fresh@example.com')
+
+        resp = self.client.post(
+            self.url,
+            data=json.dumps({'id_token': 'fake.google.jwt'}),
+            content_type='application/json',
+        )
+
+        self.assertEqual(resp.status_code, 200, resp.content)
+        body = resp.json()
+        self.assertEqual(body['email'], 'fresh@example.com')
+        self.assertEqual(body['role'], 'customer')
+        self.assertTrue(body['token'])
+
+        user = User.objects.get(email='fresh@example.com')
+        self.assertTrue(Token.objects.filter(user=user).exists())
+        # Confirm audience was passed to verify_oauth2_token
+        _, call_kwargs = mock_verify.call_args[0], mock_verify.call_args
+        self.assertEqual(mock_verify.call_args[0][2], 'test-client-id.apps.googleusercontent.com')
+
+    def test_missing_id_token_returns_400(self):
+        resp = self.client.post(
+            self.url,
+            data=json.dumps({}),
+            content_type='application/json',
+        )
+        self.assertEqual(resp.status_code, 400)
+        self.assertEqual(resp.json()['error'], 'id_token is required')
+
+    @patch('google.oauth2.id_token.verify_oauth2_token')
+    def test_invalid_token_returns_401(self, mock_verify):
+        mock_verify.side_effect = ValueError('Token audience mismatch')
+
+        resp = self.client.post(
+            self.url,
+            data=json.dumps({'id_token': 'tampered.or.wrong-aud.jwt'}),
+            content_type='application/json',
+        )
+        self.assertEqual(resp.status_code, 401)
+        self.assertEqual(resp.json()['error'], 'Invalid Google token')
+
+    @patch('google.oauth2.id_token.verify_oauth2_token')
+    def test_existing_user_reuses_token(self, mock_verify):
+        existing = User.objects.create_user(
+            username='returning@example.com',
+            email='returning@example.com',
+            password='irrelevant',
+            role='customer',
+        )
+        existing_auth_token = Token.objects.create(user=existing)
+        mock_verify.return_value = self._valid_idinfo('returning@example.com')
+
+        resp = self.client.post(
+            self.url,
+            data=json.dumps({'id_token': 'returning.user.jwt'}),
+            content_type='application/json',
+        )
+        self.assertEqual(resp.status_code, 200)
+        self.assertEqual(resp.json()['token'], existing_auth_token.key)
+        # No duplicate user created
+        self.assertEqual(User.objects.filter(email='returning@example.com').count(), 1)