Phase 1d — dogfood migration + retire legacy pipeline tab

Phase 1d closes out the Kazokus Social Publishing feature. It migrates the legacy Kazokus-internal deploy pipeline onto the productized schema, retires the old /platform/pipeline Social Drafts tab, adds management commands for dogfood enablement, lands an end-to-end integration test, and fixes a real bug in the approve flow that was silently regressed by Phase 1c's prefetch work.

After merge + production deploy, the Kazokus dogfood community uses the same promote/submit/approve/push flow that customers do.