Support encrypted .sideconf SideStore account files

[thamerszx-source]

SideStore 2.0 changed its account export twice: the JSON keys were renamed (adiPB/local_user -> anisetteAdiBlob/anisetteIdentifier), the Apple ID password became optional, and the file is now written as an encrypted .sideconf container instead of plain JSON. Importing such an export failed with an opaque JSON decoding error.

SideStoreAccount now decodes both the legacy and the 2.0 key names and treats the Apple ID password as optional. SideStoreConfigurationFile reads the .sideconf container: a 16 byte salt followed by an AES-GCM sealed box, keyed with PBKDF2-HMAC-SHA256 over the file password (10 000 iterations, 32 bytes), matching SideStore's own ImportExport.swift and scripts/sideconf/decrypt_sideconf.py.

The file type is detected by attempting to parse the payload as JSON rather than by sniffing the first byte, since a container whose salt happens to start with "{" would otherwise be misread as a legacy export.

In Settings, the importer now accepts .sideconf files, prompts for the file password when the payload is encrypted, and reports distinct errors for a wrong password, a missing field and a malformed file. When the export omits the Apple ID password, the confirmation says so instead of implying the account is ready to sign in.

FULLY CLAUDE GENERATED COMMIT, I TESTED IT.

[hugeBlack]

Thanks, however since the sidestore 0.6.4 is still under rapid development, the format of exported account might change at anytime. We might add support for encrypted sidestore account after a stable version is released.