feat(platform): add active metadata change outbox

[zhouning]

Summary

• atomically register ResourceVersion and deterministic resource_version.registered events
• add tenant/workload-scoped PostgreSQL outbox claim, retry, lease, completion, and RLS boundaries
• generate content-bound metadata_fabric.projection_plan intents without provider mutation authority
• commit PostgreSQL 16 rehearsal evidence, ADR-060, CI, runtime inventory, roadmap, and system-of-record updates

Verification

• 76 focused tests passed
• PostgreSQL 16 Active Metadata outbox rehearsal passed
• migration, gateway, platform truth, evidence, Python, YAML, JSON, and shell validation passed

Scope boundary

This is local transactional Active Metadata evidence. It does not deploy a resident consumer, submit DolphinScheduler work, authorize provider apply, execute provider mutations, or claim production ingestion/readiness.