Phase 0 — Preparation and backups - Inventory: enumerate al…

Phase 0 — Preparation and backups
- Inventory: enumerate all seeds, xprv/xpubs, derivation paths, address/script types, outstanding invoices, and any watch-only descriptors.
- Backups: export encrypted seed backups, xprv/xpub, and a CSV/JSON of all UTXOs, addresses, labels, and invoice metadata.
- Freeze policy: stop issuing new legacy addresses (or rate-limit) once dual-mode is live to reduce surface area you must migrate later.