feat: add MiniMax AI hello world tutorial in 04_hello_genai

[octo-patch]

Summary

• Add MiniMax AI as a new GenAI provider in the 04_hello_genai tutorial series
• New 03_hello_minimax directory: standalone hello world project using MiniMax's OpenAI-compatible API with M2.7 model (1M context, streaming support)
• Update existing LiteLLM example to include MiniMax via openai/ prefix routing with custom api_base

Changes

New: 04_hello_genai/03_hello_minimax/

• readme.md: Tutorial covering MiniMax API setup, key features, and getting started guide
• myproject/src/myproject/hello.py: Two functions — minimax() for standard chat completion and minimax_stream() for streaming
• myproject/pyproject.toml: Project config with openai dependency and script entry points
• myproject/tests/test_minimax_unit.py: 10 unit tests (client config, model, temperature, streaming, LiteLLM integration)
• myproject/tests/test_minimax_integration.py: 3 integration tests (chat completion, streaming, highspeed model)

Updated: 04_hello_genai/02_litellm/

• Added minimax() function using LiteLLM's OpenAI-compatible routing
• Updated pyproject.toml with minimax script entry
• Updated readme.md with MiniMax API key setup and code example

Why MiniMax?

MiniMax offers powerful LLMs with an OpenAI-compatible API, making it easy for students to try an alternative provider. The M2.7 model features a 1M token context window and strong multilingual capabilities.

Test plan

• All 10 unit tests pass
• All 3 integration tests pass (real MiniMax API calls)
• Verify uv run minimax and uv run minimax_stream work as documented