Multi-Provider AI Model Selector:
- Added ModelSelectorDialog to add, edit, delete and set active AI models
- Support for Mistral, OpenAI, Groq, Ollama and any OpenAI-compatible API
- Model configurations (endpoint, API key, model name, temperature, max tokens) stored in QSettings
- Refactored MistralAPI to be provider-agnostic with dynamic model loading
- Added "Check AI Model Status" menu option showing active model details
- Informational tooltip listing compatible and incompatible providers
