DOC: Archive after ingestion into ITK main

The TotalVariation module is now maintained in ITK main at
Modules/Filtering/TotalVariation (ingested via
InsightSoftwareConsortium/ITK#6381; the bundled proxTV dependency now
lives at Modules/ThirdParty/proxTV). Delete whitelisted sources, rename
README.rst to info.rst, and promote the migration notice to README.md so
the GitHub landing page shows archived status.

Author: hjmjohnson

CMakeLists.txt

@@ -0,0 +1,13 @@
+# Migrated to ITK main
+
+The `TotalVariation` module has been ingested into the Insight Toolkit (ITK) main repository and is no longer maintained here.
+
+- **In-tree location:** [`Modules/Filtering/TotalVariation`](https://github.com/InsightSoftwareConsortium/ITK/tree/main/Modules/Filtering/TotalVariation)
+- **Ingest PR:** [InsightSoftwareConsortium/ITK#6381](https://github.com/InsightSoftwareConsortium/ITK/pull/6381)
+- **Merge commit:** [`3609b55578`](https://github.com/InsightSoftwareConsortium/ITK/commit/3609b5557840454bb83527fb2e88684474841b2a)
+
+The bundled `proxTV` dependency is now provided in ITK main as the `Modules/ThirdParty/proxTV` third-party module.
+
+Future development, bug fixes, and pull requests should target ITK main. This repository's history is preserved for `git blame` and archival reference. The original module description is preserved in [`info.rst`](info.rst).
+
+**Maintainer action:** this repository is **Archived** (read-only). See the [ITK ingestion strategy](https://github.com/InsightSoftwareConsortium/ITK/blob/main/Utilities/Maintenance/RemoteModuleIngest/INGESTION_STRATEGY.md) for context.