feat: set up Python project structure with pyproject.toml

- Add pyproject.toml with core and dev dependencies
- Configure Ruff for linting and formatting
- Configure MyPy for strict type checking
- Configure pytest with asyncio support
- Create src/polymarket_insider_tracker package structure
- Add py.typed marker for PEP 561 compliance
- Add pre-commit hooks configuration
- Add comprehensive .gitignore
- Create test directory structure with basic tests

Closes #25

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/conftest.py

@@ -0,0 +1,9 @@
+"""Pytest configuration and fixtures."""
+
+import pytest
+
+
+@pytest.fixture
+def sample_market_id() -> str:
+    """Sample market ID for testing."""
+    return "0x1234567890abcdef1234567890abcdef12345678"