refactor(QED): name even anomaly-cancellation planes

[catlover-bot]

Summary

• name the two even anomaly-cancellation planes Unshifted and Shifted, following the terminology introduced for the odd case in refactor(QED): name odd anomaly-cancellation planes #1502
• move the corresponding basis and plane APIs under Unshifted / Shifted namespaces, including basisAsCharges, basis, planeCharges, and planeLinSols
• update references and documentation in Even/LineInCubic.lean and Even/Parameterization.lean
• keep the mathematical content unchanged

Contributes to #1046.

Validation

• lake build +Physlib.QFT.QED.AnomalyCancellation.Even.BasisLinear +Physlib.QFT.QED.AnomalyCancellation.Even.LineInCubic +Physlib.QFT.QED.AnomalyCancellation.Even.Parameterization
• ./scripts/lint-style.sh
• lake build (9269 jobs)

[github-actions]

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[jstoobysmith]

Added some small comments about some names which probably could also do with being updated.

[jstoobysmith]

awaiting-author

[catlover-bot]

-awaiting-author

[jstoobysmith]

Many thanks - approved. Assuming the linters pass, I will merge