refactor: use compas_cgal.isolines for contour extraction

[jf---]

Summary

• replace python edge-crossing detection with CGAL isolines backend
• add GeodesicContours class using geodesic_isolines directly
• remove backwards compat aliases from geodesics.py (245→49 lines)
• detect mesh boundaries from topology instead of JSON files

Test plan

• all functional tests pass
• examples run correctly

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• only merge after fix CI: ruff compliance, dep versions, remove rdp #182 is merged
• requires as of yet unreleased in compas_cgal