Hardware Wallet Data Backup & Restore

[ovitrif]

Part of #998.

Blocked by synonymdev/bitkit-core#113. Also depends on the final activity model shape from synonymdev/bitkit-core#112.

Scope

Update the app's backup/restore flow after Core exposes wallet-scoped activity migration/export APIs.

Current app state:

• ActivityBackupV1 stores Core-owned activities: List<Activity>, activityTags: List<ActivityTags>, and closedChannels: List<ClosedChannelDetails>.
• MetadataBackupV1 stores Core-owned tagMetadata: List<PreActivityMetadata> alongside app-owned cache/pubky data.
• BackupRepo currently decodes those payloads directly into generated Core models before Core can migrate legacy activity JSON.
• Core owns the activity data and activity DB. The app owns the VSS envelope, backup scheduling, and backup status.

Required app changes

After synonymdev/bitkit-core#113 lands:

• Read the ACTIVITY and METADATA VSS backup envelopes without decoding Core-owned fields into generated Core models first.
• Pass raw Core-owned activity/tag/pre-activity metadata JSON to Core migration/import APIs.
• Keep app-owned restore work in the app, including cache, pubky session, settings, widgets, wallet records, and backup status handling.
• Ask Core for migrated/current Core-owned backup entries after migration/import.
• Rewrite the app-owned VSS backup envelopes with those migrated/current Core entries so the next restore no longer depends on legacy model JSON.
• Do not add app-owned v1/v2 walletId migration semantics for Core models.

Acceptance criteria

• A legacy activity backup whose Core activity/tag/metadata entries are missing walletId restores through Core migration without app-side JSON patching.
• The app rewrites the ACTIVITY and affected METADATA VSS backups with migrated/current Core entries after migration.
• Future restores decode the rewritten VSS backups without requiring the legacy migration path.
• Existing non-default wallet ids returned by Core are preserved in rewritten backups.
• Tests cover legacy ActivityBackupV1 and MetadataBackupV1 restore input, the Core migration/import call boundary, and VSS backup rewrite behavior.