Backup compatibility

0.5.3 (2026-08-04)

Backup compatibility

• Phone and desktop now share one backup/import implementation: the Android app and the desktop GUI both use the single Rust export_vault_dirs / restore_backup_to_dirs code path, so backups move between platforms with no format differences.
• Fixed phone → desktop backup import (crypto error: key unwrap failed): phone backups now include a params.toml recording the exact Argon2id parameters used to wrap the master key. Restoring overwrites any stale desktop params.toml, so the GUI always derives the correct key.
• Phone no longer hardcodes KDF parameters: RustKeyManager writes and reads params.toml (its own 16384/3/2 settings), while remaining compatible with desktop vaults (19456/2/2).
• Round-trip tests: phone↔GUI backup compatibility is now covered in Rust (phone_roundtrip), through the real GUI code path (vault.rs), and with Kotlin unit tests for the params.toml builder/parser.

Backup import now merges

• Import Backup merges instead of replacing (desktop GUI and Android): existing documents, collections, and tags are preserved, and the backup's content is added on top. When a document already exists with different content, the local one is kept with a conflict flag and the backup's version is added as a copy.
• The local passkey stays unchanged: merging keeps the current vault open under its own passkey; only the backup's own passkey is needed to decrypt it, so backups created with a different passkey can be merged and are re-encrypted with the local key.
• Merged documents are full-text searchable: text content is carried over from the backup.
• Fixed backup import failing on Android (Permission denied): the temporary database is now written inside the app's own storage instead of the system temp directory.
• Fresh installs still restore wholesale: when there is no local vault (fresh install/reinstall), the backup is restored exactly as before and the app opens the unlock screen.
• Merge tests: cross-passkey merge covered in Rust (test_merge_backup_to_vault_cross_password, test_merge_backup_into_existing_library_cross_password) and with Android instrumented tests; the document-type library test now tolerates thumbnails.