uv project structure

Standard uv project structure:

```
myproject/
├── pyproject.toml # Project config and dependencies
├── uv.lock # Locked dependencies (commit this!)
├── .python-version # Python version (e.g., "3.12")
├── src/
│ └── myproject/
│ ├── __init__.py
│ └── main.py
└── tests/
└── test_main.py
```

Key files:
- `pyproject.toml`: Define dependencies here, not requirements.txt
- `uv.lock`: Always commit - ensures reproducible builds
- `.python-version`: uv auto-installs the correct Python version