Default OpenAI provider for baibot to use `gpt-image-1` instead of `dall-e-3`

Ref:

- d2660be33c/CHANGELOG.md (2025-05-10-version-170)
- https://openai.com/index/image-generation-api/

roles/custom/matrix-bot-baibot/defaults/main.yml

@@ -389,8 +389,8 @@ matrix_bot_baibot_config_agents_static_definitions_openai_config_text_to_speech_
 matrix_bot_baibot_config_agents_static_definitions_openai_config_text_to_speech_response_format: opus
 
 matrix_bot_baibot_config_agents_static_definitions_openai_config_image_generation_enabled: true
-matrix_bot_baibot_config_agents_static_definitions_openai_config_image_generation_model_id: dall-e-3
-matrix_bot_baibot_config_agents_static_definitions_openai_config_image_generation_style: vivid
+matrix_bot_baibot_config_agents_static_definitions_openai_config_image_generation_model_id: gpt-image-1
+matrix_bot_baibot_config_agents_static_definitions_openai_config_image_generation_style: null
 matrix_bot_baibot_config_agents_static_definitions_openai_config_image_generation_size: 1024x1024
 matrix_bot_baibot_config_agents_static_definitions_openai_config_image_generation_quality: null