docs: plan retirement of legacy backend python cli

plans/harborforge-cli-go-plan.md

@@ -1031,6 +1031,19 @@ The backend should support:
 
 ---
 
+## Legacy Python CLI Retirement
+
+After the new `hf` CLI is complete and functionally replaces the old workflow, the old Python CLI in the backend project should be removed.
+
+That means:
+- remove the legacy backend CLI implementation (currently under `HarborForge.Backend`)
+- update backend docs so they no longer point users to the old Python CLI
+- treat the Go-based `hf` binary as the canonical HarborForge CLI going forward
+
+This removal should happen only after the new CLI is sufficiently complete for the intended workflows.
+
+---
+
 ## Non-Goals (for now)
 
 - do not directly port the old Python CLI architecture