Extend sync crypto to support byte arrays

[CDRussell]

Task/Issue URL: https://app.asana.com/1/137249556945/project/72649045549333/task/1212290226255081?focus=true

Description

Adds sync crypto support for byte arrays, adding the ability to encrypt and decrypt them similar to the existing functions which support strings only.

There's a few extra changes required because of needing to extend the test suite, as well as a few FakeCrypto implementations for testing, each needing tweaked.

But the core change is:

• add the new APIs which accept a byte array
• change the existing APIs to first convert String -> Byte Array as they are doing now already, then invoke the other function so that the logic is shared between the two impls.

Steps to test this PR

• QA optional
• Can smoke test sync still works ok; e.g., set up two devices and update a password on one of them, make sure it syncs

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Note

Adds ByteArray encrypt/decrypt APIs to sync crypto, implements them in native and real crypto, and updates tests and fakes accordingly.

• API
  • Extend SyncCrypto with encrypt(data: ByteArray) and decrypt(data: ByteArray); clarify string encrypt returns Base64.
• Implementation
  • RealSyncCrypto: implement new ByteArray methods with error recording; keep string methods; early-return on empty inputs.
• Native library
  • SyncLib/SyncNativeLib: add ByteArray overloads for encryptData/decryptData and wire through SyncNativeLibImpl.
  • Introduce EncryptBytesResult and DecryptBytesResult; adapt string methods to reuse ByteArray flow.
• Tests
  • SyncCryptoTest: add ByteArray encrypt/decrypt tests and adjust string tests.
  • Update FakeCrypto in tests (app, autofill, saved-sites, sync-settings) to implement new ByteArray methods.

^{Written by Cursor Bugbot for commit 610d556. This will update automatically on new commits. Configure here.}

[CDRussell]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Allow duck ai chat syncing (Internal) #7377
• Extend sync crypto to support byte arrays #7375 👈 (View in Graphite)
• Include duck AI chat deletions in sync engine #7354
• Update sync APIs to support deletions #7340
• develop

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[malmstein]

SHIP IT

[cursor]

Bug: Test verification never executes due to preceding exception

The verify(recorder).record(...) statements in whenEncryptByteArrayFailsThenExceptionThrown and whenDecryptByteArrayFailsThenExceptionThrown are placed after the line that throws an exception. Since syncCrypto.encrypt()/decrypt() throws before reaching the verification, these assertions never run. The tests will pass even if the recorder is never called in production, potentially masking missing error recording behavior.

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Additional Locations (1)

• sync/sync-impl/src/test/java/com/duckduckgo/sync/impl/SyncCryptoTest.kt#L126-L134