Motivation

• Users reported that generated images sometimes do not appear in the browser, so the preview should render even when the static outputs URL is inaccessible or cached incorrectly.

Description

• Backend now Base64-encodes the generated SVG preview and returns a data_url in the generation response by extending GeneratorService.generate and changing _create_preview_svg to return (Path, str) in backend/app/generator.py.
• Frontend now prefers the returned data_url when setting resultImage.src and falls back to the cache-busted file_url if data_url is not present in frontend/app.js.
• The API contract was extended by adding data_url to the GenerationResult model and the unit test tests/test_api.py was updated to assert the presence of the data_url field.
• Modified files: backend/app/generator.py, frontend/app.js, and tests/test_api.py.

Testing

• Ran unit tests with pytest -q, which completed successfully and reported 3 passed.
• Updated API test asserts the new data_url field and its data:image/svg+xml;base64, prefix.

Codex Task