updated for pyqt6

[pariterre]

This change is 

[Copilot]

Pull Request Overview

This PR updates the codebase to use PyQt6 instead of PyQt5, modernizing the Qt framework dependency and updating all related imports and API calls.

• Updates PyQt dependency from PyQt5 to PyQt6 (>=6) in environment configuration
• Migrates all PyQt5 imports to PyQt6 equivalents across visualization, analysis, and UI components
• Updates Qt API calls to use PyQt6's enum-based approach for constants and properties

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
environment.yml	Updates PyQt dependency specification to require version 6 or higher
bioviz/viz.py	Migrates PyQt5 imports to PyQt6 and updates Qt constant usage to enum-based syntax
bioviz/qt_ui/rectangle_on_slider.py	Updates PyQt imports and color constants to PyQt6 equivalents
bioviz/biorbd_vtk.py	Changes PyQt5 imports to PyQt6 for QtWidgets and QtGui modules
bioviz/analyses/muscle_analyses.py	Comprehensive refactor with PyQt6 migration and enhanced muscle analysis functionality
bioviz/analyses/ligament_analyses.py	Updates PyQt imports and frame shape constant usage for PyQt6 compatibility
bioviz/analyses/c3d_editor_analyses.py	Migrates PyQt5 imports and alignment constants to PyQt6 enum-based syntax

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