Migrated to ITK main

As of 2026-05-05, the PolarTransform module has been ingested into the main ITK repository at Modules/Filtering/PolarTransform and the standalone remote module is no longer maintained here.

• In-tree home: https://github.com/InsightSoftwareConsortium/ITK/tree/main/Modules/Filtering/PolarTransform
• Ingest PR: InsightSoftwareConsortium/ITK#6211
• Historical reference: the original commit history of this repository remains reachable here. The original README.rst content is preserved as info.rst.

Please file new issues and pull requests against the in-tree module.