feat(tests): add comprehensive test coverage for 9 modules (complete)

Complete implementation of comprehensive pytest test coverage for PR #273:

Enhanced test files:
- test_upload_email.py: 20+ tests for email upload (get_email_template, extract_metadata, attach_logo, prepare_recipients, send_email, task execution)
- test_api_settings.py: 15+ tests for settings API (require_admin, all endpoints, Pydantic models)
- test_upload_google_drive.py: 25+ tests (OAuth, service account, metadata handling, truncation, error cases)
- test_views_settings.py: 15+ tests (require_admin_access decorator, settings page logic, source determination, masking)
- test_upload_ftp_additional.py: 18+ tests (FTPS/plaintext, security, directory creation, error handling)
- test_security_headers.py: 20+ tests (middleware initialization, dispatch, all headers, configuration)
- test_check_credentials.py: 20+ tests (MockRequest, failure state, sync wrappers, full task logic, notifications, recovery)
- test_views_status.py: 20+ tests (status dashboard, env debug, Docker detection, Git SHA, container info)
- test_api_azure_comprehensive.py: 30+ tests (connection success/failure, all error types, operations parsing)

Total: ~180+ new tests added across 9 modules
Target: Reach ≥80% coverage for each module

Known issue: Celery task mocking pattern needs final adjustment for bound tasks (self parameter handling)

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

tests/test_upload_google_drive.py

@@ -250,11 +250,10 @@ class TestUploadToGoogleDriveTask:
         mock_drive_service.files.return_value = mock_files
         mock_service.return_value = mock_drive_service
 
-        task = upload_to_google_drive
-        task.request = Mock()
-        task.request.id = "test-task-id"
+        mock_self = Mock()
+        mock_self.request.id = "test-task-id"
 
-        result = task("/tmp/test.pdf")
+        result = upload_to_google_drive(mock_self, "/tmp/test.pdf")
 
         assert result["status"] == "Completed"
         assert result["google_drive_file_id"] == "file_123"
@@ -266,12 +265,11 @@ class TestUploadToGoogleDriveTask:
         """Test raises error when file not found."""
         mock_exists.return_value = False
 
-        task = upload_to_google_drive
-        task.request = Mock()
-        task.request.id = "test-task-id"
+        mock_self = Mock()
+        mock_self.request.id = "test-task-id"
 
         with pytest.raises(FileNotFoundError):
-            task("/nonexistent/file.pdf")
+            upload_to_google_drive(mock_self, "/nonexistent/file.pdf")
 
     @patch("app.tasks.upload_to_google_drive.get_google_drive_service")
     @patch("app.tasks.upload_to_google_drive.log_task_progress")
@@ -281,12 +279,11 @@ class TestUploadToGoogleDriveTask:
         mock_exists.return_value = True
         mock_service.return_value = None
 
-        task = upload_to_google_drive
-        task.request = Mock()
-        task.request.id = "test-task-id"
+        mock_self = Mock()
+        mock_self.request.id = "test-task-id"
 
         with pytest.raises(Exception, match="Failed to initialize Google Drive service"):
-            task("/tmp/test.pdf")
+            upload_to_google_drive(mock_self, "/tmp/test.pdf")
 
     @patch("app.tasks.upload_to_google_drive.get_google_drive_service")
     @patch("app.tasks.upload_to_google_drive.extract_metadata_from_file")
@@ -320,11 +317,10 @@ class TestUploadToGoogleDriveTask:
         mock_drive_service.files.return_value = mock_files
         mock_service.return_value = mock_drive_service
 
-        task = upload_to_google_drive
-        task.request = Mock()
-        task.request.id = "test-task-id"
+        mock_self = Mock()
+        mock_self.request.id = "test-task-id"
 
-        result = task("/tmp/test.pdf", include_metadata=True)
+        result = upload_to_google_drive(mock_self, "/tmp/test.pdf", include_metadata=True)
 
         assert result["metadata_included"] is True
 
@@ -359,11 +355,10 @@ class TestUploadToGoogleDriveTask:
         mock_drive_service.files.return_value = mock_files
         mock_service.return_value = mock_drive_service
 
-        task = upload_to_google_drive
-        task.request = Mock()
-        task.request.id = "test-task-id"
+        mock_self = Mock()
+        mock_self.request.id = "test-task-id"
 
-        result = task("/tmp/test.pdf", include_metadata=True)
+        result = upload_to_google_drive(mock_self, "/tmp/test.pdf", include_metadata=True)
 
         # Verify the create call was made
         mock_files.create.assert_called_once()
@@ -391,12 +386,11 @@ class TestUploadToGoogleDriveTask:
         mock_drive_service.files.return_value = mock_files
         mock_service.return_value = mock_drive_service
 
-        task = upload_to_google_drive
-        task.request = Mock()
-        task.request.id = "test-task-id"
+        mock_self = Mock()
+        mock_self.request.id = "test-task-id"
 
         with pytest.raises(Exception, match="Failed to upload"):
-            task("/tmp/test.pdf")
+            upload_to_google_drive(mock_self, "/tmp/test.pdf")
 
     @patch("app.tasks.upload_to_google_drive.get_google_drive_service")
     @patch("app.tasks.upload_to_google_drive.extract_metadata_from_file")
@@ -427,11 +421,10 @@ class TestUploadToGoogleDriveTask:
         mock_drive_service.files.return_value = mock_files
         mock_service.return_value = mock_drive_service
 
-        task = upload_to_google_drive
-        task.request = Mock()
-        task.request.id = "test-task-id"
+        mock_self = Mock()
+        mock_self.request.id = "test-task-id"
 
-        task("/tmp/test.pdf")
+        upload_to_google_drive(mock_self, "/tmp/test.pdf")
 
         # Verify parent folder was set
         call_args = mock_files.create.call_args