- Add `SymmetricallyDecrypt` to `pkg/crypt/std/pgp`.
- Add validation for empty passphrases in `SymmetricallyEncrypt` and `SymmetricallyDecrypt`.
- Refactor `pkg/crypt/std/pgp/pgp.go` to use package-level variables for `openpgp` functions to enable mocking.
- Add comprehensive tests in `pkg/crypt/std/pgp/pgp_test.go` to cover error paths using mocks, achieving 100% coverage.
- Remove practically unreachable error check in `GenerateKeyPair` for `SignUserId` (as `NewEntity` guarantees validity).
This commit introduces a full OpenPGP implementation in `pkg/crypt/std/openpgp`, using the ProtonMail `go-crypto` library.
The new `openpgp.Service` provides a clean, Web3-friendly API for PGP operations, including:
- Key pair generation
- Subkey management
- Encryption and decryption of messages
- Signing and verification of messages
The implementation is based on the user's `Core` repository and uses file-based key management. The main `crypt.Service` has been updated to integrate and expose this new functionality.
