- BREAKING: SDK constraint bumped to >=3.0.0 <4.0.0
- Replace `lint` with `flutter_lints: ^5.0.0`
- Remove deprecated `strong-mode` analyzer options
- Migrate CI from Travis to GitHub Actions (ci.yml + web-demo.yml)
- Add .mise.toml (Flutter 3.35.7) and .pubignore to version control

Bug fixes:
- Fix division by zero in normalizeValue when minValue == maxValue
- Fix shouldRepaint only checking value — now compares full style equality
- Fix null dereference on IconTheme.size (fallback to 24.0)
- Fix threshold comparison: bars now active when value >= threshold (was >)
- Add clamping in normalizeValue to 0.0–1.0 range
- Fix user-provided levels silently discarded when count != barCount
- Move clipRect outside loop in sector painter
- Fix variable shadowing (offset → roundedOffset) in sector painter
- Remove redundant imports (widgets.dart, cupertino.dart)
- Update constructors to super.key / super parameter style

Tests:
- Fix sector test group label ('Bar' → 'Sector')
- Remove unused bar_fixture import in sector tests
- Delete orphan test/goldens/bars-threshold.png
- Add test/util_test.dart and test/style_test.dart (12 unit tests)
- Regenerate all golden files

Docs:
- Update README: new badges, requirements section, full parameter table,
  expanded usage examples with levels, custom ranges, and styling options
- Update CHANGELOG with v0.5.0 entry