feat(account): command handlers for account management (task 21)

[mpiton]

Summary

• Implement 6 command handlers: add, update, delete, validate, import, export
• Add domain ports: AccountValidator, AccountCredentialStore, PassphraseCodec
• Implement KeyringAccountStore and AesGcmPbkdf2Codec adapters
• Add 7 domain events for account operations
• Full test coverage: 91-97% handlers, 95% codec

Type

feat

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Summary by cubic

Adds six account command handlers and crypto/keyring plumbing for full account management and encrypted import/export. Implements task 21 with atomic, cross‑platform‑safe exports and stronger rollback/cleanup on keyring failures.

• New Features

  • Handlers: add, update, delete, validate, export, import.
  • Ports: AccountValidator (+ ValidationOutcome), AccountCredentialStore, PassphraseCodec.
  • Adapters: KeyringAccountStore (per-account passwords), AesGcmPbkdf2Codec (AES‑256‑GCM + PBKDF2; header as AAD).
  • Events via Tauri: account-added/updated/deleted/validated/validation-failed/accounts-imported/accounts-exported.
  • CommandBus wired with builders for the new ports; handlers validate inputs and keep DB/keyring in sync.
  • Dependencies: aes-gcm, pbkdf2, hmac, rand.

• Bug Fixes

  • add_account: on keyring write failure, roll back row, best‑effort delete partial secret, and log rollback errors.
  • update_account: on rotation failure, roll back row and restore the previous password (or delete if none).
  • delete_account: keyring delete is best‑effort so AccountDeleted always fires.
  • export_accounts: write to a temp file, fsync, then perform a single atomic rename to replace the destination; always clean up the temp file.
  • import/validate hardening: cap PBKDF2 iterations; trim inputs and skip duplicates; atomically roll back the whole batch on any entry failure (including a failed keyring write); emit AccountValidationFailed for transport/storage errors.
  • Preserve created_at across export/import so list ordering remains stable.
  • Tests: rename the test passphrase fixture to avoid secret-scanner false positives (no behavior change).

^{Written for commit c0a8154. Summary will update on new commits. Review in cubic}

Summary by CodeRabbit

• New Features

  • Account management: add/update/delete accounts with per-account OS keyring credential storage and automatic rollback on secret-store failures
  • Account validation: test credentials, persist validation metadata (timings/traffic/valid-until) and emit success/failure events
  • Encrypted bundles: export/import accounts to an authenticated passphrase format (AES‑GCM + PBKDF2), with pre-validation and duplicate skipping

• Events

  • UI-facing account lifecycle and import/export events emitted

• Documentation

  • CHANGELOG expanded with account, credential, and export/import details