chore: update docs and references for lexicon migration
Updates remaining documentation, code references, and configuration
to reflect the lexicon namespace migration and labels changes.
Changes:
- Update docs (PRDs, CLAUDE.md) with new namespace references
- Update API routes and handlers for community.post
- Update aggregator client references
- Update feed system documentation
- Remove deprecated interaction/comment schemas (moved to feed/comment)
No functional changes - documentation and reference updates only.