Enhance Seed Handling: Support Both Hex and BIP39 Mnemonic Import

[JFixby]

Description

This PR updates the Seed function to improve wallet setup and restore experience.

Changes

• When generating a new seed:
  • Seed is displayed in hex format.
  • Seed is also displayed as a BIP39 mnemonic.
  • Original entropy and derived seed are displayed.
• When restoring an existing wallet:
  • User can now enter either a hexadecimal seed or a BIP39 mnemonic phrase.
• Validation added for both input types.
• User flow is preserved (prompt for "OK" confirmation before proceeding).

Motivation

• Allow interoperability: users can restore wallets using their mnemonic across different wallets (Electrum, BlueWallet, Sparrow, etc).

Dependencies

• Adds a dependency on github.com/tyler-smith/go-bip39 for BIP39 mnemonic support.

Example Usage

New wallet flow:

Do you have an existing wallet seed you want to use? (no): no
> Your wallet mnemonic phrase (VERY IMPORTANT):
> "squirrel envelope moon ..."
>
> Original entropy used (hex):
> a1b2c3...
>
> Derived seed (hex) from mnemonic (for wallet generation):
> 89abcdef...
>
> IMPORTANT: Keep the mnemonic and entropy in a safe place as you
> you will NOT be able to restore your wallet without them.
> Anyone with access to the mnemonic or seed can restore your wallet
> and access all your funds, so it is critical to store it securely.
>
> (User types OK after saving)

Restore wallet flow from mnemonic:

Do you have an existing wallet seed you want to use? (no): yes
> Enter mnemonic or hex: "squirrel envelope moon ..."
> Wallet restored from mnemonic!

Restore wallet flow from hex seed:

Do you have an existing wallet seed you want to use? (no): yes
> Enter mnemonic or hex: "89abcdef..."
> Wallet restored from hex seed!

[JFixby]

Fixing #730