feat(viz): add Plotly visualization backend

[PierreRaybaut]

Summary

• add dependency-free Plotly JSON figure builders and an optional interactive backend
• render canonical annotations, ROIs, masks, and geometry results in Plotly figures
• migrate supported historical PlotPy annotations without importing PlotPy
• document the backend and package Plotly as an optional dependency

Validation

• focused Plotly and migration tests: 37 passed
• full Sigima suite: 1490 passed, 30 skipped
• Ruff format and lint checks passed
• Pylint completed with zero enabled diagnostics (10.00/10)
• English and French Sphinx HTML builds passed with warnings treated as errors
• wheel and source distribution builds passed; Plotly metadata, new modules, and the annotation schema were verified in the archives

Dependency

This PR depends on #56, which has been merged into the develop branch.