Support for multiple SLIP-0021 paths not available

[miketlk]

Description

The application requires the ability to specify more than one SLIP-0021 path for proper functionality, but the current app database only supports a single path.

For example, the new Liquid Network application needs two SLIP-0021 paths:

• "LEDGER-Wallet policy": Used to register non-standard wallets, aligning with the mechanism of the Bitcoin app.
• "SLIP-0077": Required to derive the master blinding key from the seed.

Currently, the "path_slip21" field only accepts a single path, which limits the application's functionality and compatibility with existing wallet policies and blinding key derivation requirements.

Proposed Solution

Allow the "path_slip21" field to support multiple paths as a string array or in some other form, enabling applications to define distinct paths for different purposes.