Wallet Backup Provider
interface WalletBackupProvider
Interface for modular wallet backup storage providers.
This abstraction allows for different backup backends:
LocalFileBackupProvider: App files directory (auto-synced by Google Backup / iCloud)
CloudKeychainProvider: Direct iCloud Keychain / Google Backup API (future)
ExportFileProvider: User-managed export file (future)
ServerCloudProvider: MPC managed share (future) (mpc-client-sdk library)
EmailRecoveryProvider: Email-based recovery (future)
All providers store ENCRYPTED data - they never see plaintext keyshares. The encryption/decryption is handled by BackupEncryption before calling these methods.