Release 0.3.3

What's Changed

Performance

• Persistent HTTP session reuse across API calls (avoids repeated connection overhead)
• Retries enabled by default (retry_attempts=3 with exponential backoff for transient errors)

Fixes

• Correct sportTypeId for swimming workouts
• Ruff and mypy CI clean (0 errors)

Misc / Tooling

• Added -debug / -d flag on demo script for timing and HTTP visibility
• Python 3.12 minimum; tooling and workout models modernized
• Expanded mocked unit test coverage (~30 new tests)