WORK-019 - Simplify Device Backup

Feature: FEAT-006-device-key.md Status: In Progress

Tasks

1. Replace legacy secure-storage layouts
- Files: lib/services/settings_service.dart, lib/services/device_key_service.dart
- Create the settings, temp_settings, nwc, device_key, and amber_pubkey layout; intentionally do not migrate existing values.
2. Create portable device-state persistence
- Files: lib/services/device_private_event_service.dart, lib/services/device_private_sync_service.dart, new state service
- Persist portable state locally, self-encrypt and publish 30078/zapstore-device-state, and fold in trusted signers.
3. Implement bootstrap admission
- Files: lib/main.dart, device-state/private-event services, device-key UI
- Mine the first empty device-state event at 28-bit PoW in the background isolate; queue later private publications, disable settings until accepted, and cancel only on lifecycle disposal.
4. Replace capsule recovery with Amber key backup
- Files: lib/services/device_backup_service.dart, lib/widgets/device_backup_dialog.dart, lib/screens/profile_screen.dart
- Publish Amber-authored 30078/zapstore-device-key-backup, restore via Amber or pasted nsec, and route absent Amber to its install page.
5. Add legacy installed-app recovery
- Files: app restore UI, package/install orchestration, temp_settings
- During incomplete restore onboarding and Amber sign-in, offer apps from a non-empty legacy Amber zapstore-installed-apps stack without treating them as installed or overwriting them with an empty device stack.
6. Remove obsolete paths
- Delete capsule authorization, recovery-candidate, trusted-signers event, old settings-event, and migration-marker logic.
7. Add release warning and tests
- Warn current users that all old secure storage is discarded and nsec must be copied before upgrade. Cover schema, restore, bootstrap, offline/error, lifecycle cancellation, Amber-install routing, and recovery-install UI.
8. Self-review against INVARIANTS.md

Test Coverage

Scenario	Expected	Status
New key bootstrap	Empty state is first accepted private event	[ ]
Bootstrap pending	Settings disabled; local UI remains responsive	[ ]
Bootstrap lifecycle disposal	Mining isolate is cancelled without leaking	[ ]
Settings publish failure	Local portable state remains available; retry is explicit	[ ]
Pasted nsec restore	Signature-verified state and stacks restore	[ ]
Amber restore	Verified Amber backup imports the same nsec	[ ]
Amber absent	Restore UI opens Amber install page	[ ]
Legacy installed backup	User selects apps to install; none are falsely installed	[ ]
NWC/temp exclusion	Neither is serialized to device state	[ ]
1.0.6 update	Old values are discarded after explicit warning	[ ]

Decisions

2026-07-14 - Fixed bootstrap proof

Context: Per-update proof mining makes normal settings changes expensive. Options: Mine every replacement; await a relay proof challenge; bootstrap once. Decision: Mine an empty device-state event at fixed 28-bit difficulty before any remote private write, then rely on relay admission and rate limiting. Rationale: It gives the relay a simple first-event cost while ordinary settings writes remain local-first and cheap.

2026-07-14 - No user cancellation or timeout

Context: Bootstrap is setup work, not an interruptible user operation. Decision: Show indefinite progress without timeout or a cancel button. Rationale: Avoids retry and partial-state UI complexity. The owning service/provider still cancels the isolate on disposal, as required for lifecycle safety.

Spec Issues

None

Progress Notes

2026-07-14: Contract rewritten for a clean-break migration. Relay changes are tracked separately; this work assumes it admits the first private event only when its NIP-13 difficulty is at least 28 bits.

2026-07-14: Implemented separate secure-storage entries, portable device-state persistence, 28-bit bootstrap admission, nsec parsing, and the Amber-authored key-backup record. Verification is blocked because the checked out workspace has no ../purplebase path dependency.

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