- Expand poster image model settings with provider, model name, API key,
and base URL fields (was only model name + API key)
- Add presets for OpenAI (gpt-image-1), Doubao (火山引擎), and Zhipu (CogView)
- Refactor image_generator.py to read config from system_settings DB instead
of hardcoding gpt-image-1 and OPENAI_API_KEY env var
- All OpenAI-compatible image APIs work via configurable base URL
- Add doubao and cogview to brand name mapping
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>