v1.6.9

feat(ai-integrations): add model fetching and update default models

- Add "Fetch Models" functionality to dynamically retrieve available models from AI providers
- Add internationalization strings for fetch models UI and error handling (en-US and zh-CN)
- Update default model IDs to latest versions across all providers (OpenAI, Qwen, DeepSeek, etc.)
- Add model combobox component with dropdown UI, styling, and interactions
- Implement model dropdown with search, selection, and clear functionality
- Add error handling for various HTTP status codes (401, 403, 404, 408, 429) and network errors
- Add spinning animation and UI states for loading during model fetch operations
- Improve user experience by allowing automatic model discovery instead of manual entry