Fix import without Plotly for 0.4.1

[ginitheclaw]

Summary

• bump version to 0.4.1
• keep pe.browse() available, but import the experimental browser lazily so import pyrangeyes does not require Plotly
• raise a clear optional-dependency message only when pe.browse() is called without Plotly installed
• remove unmaintained browser regression/interactive tests for now
• clean up unused imports flagged by ruff

Tests

• simulated missing Plotly with an import blocker: import pyrangeyes succeeds; pe.browse(...) raises the optional-dependency message
• .venv/bin/ruff check src tests
• .venv/bin/python -m pytest tests -q
• .venv/bin/sphinx-build -b html docs docs/_build/html