Argument --llm argument to main.py too

[Romamo]

To specify the LLM provider and model, use the --llm argument in the format Provider:Model (e.g., Openai:gpt-4, Ollama:llama3). This will override the interactive model selection.

# With Poetry:
poetry run python src/main.py --ticker AAPL,MSFT,NVDA --llm Openai:gpt-4
poetry run python src/main.py --ticker AAPL,MSFT,NVDA --llm Ollama:llama3

# With Docker (on Linux/Mac):
./run.sh --ticker AAPL,MSFT,NVDA --llm Openai:gpt-4

# With Docker (on Windows):
run.bat --ticker AAPL,MSFT,NVDA --llm Openai:gpt-4

If you do not specify --llm, you will be prompted to select a provider and model interactively.

README also updated