Private notes are not filtered by account

The `requestPrivateNotes` endpoint does not filter for the active account when returning private notes.

Bug description
The wallet should separate private notes for the different accounts. Notes imported for the account A shouldn't be visible when the account B connected

How can this be reproduced?
Create the empty wallet A (an extension reinstall is required). Use the [miden faucet](https://faucet.testnet.miden.io/) to generate a private note and import it with the wallet UI or [demo app](https://demo.miden.fi/importPrivateNote)

Visit the [demo app](https://demo.miden.fi/privateNotes) with connected wallet A and request private notes with filter All. The single note should be visible.

Create the account B in the wallet UI. Disconnect the wallet A from the demo app and connect the wallet B. Refresh the page. Request the private notes again. The same note will be visible.

Find the `requestPrivateNotes` endpoint in the codebase, likely in a service or API module. Understand how private notes are stored and retrieved, and how the active account is identified. The fix involves adding account-based filtering to the note retrieval logic. Test by reproducing the steps in the bug description using the demo app.

Written by the indexing model from the issue text.