fix(wallet): set Argon2 derived bytes for AES IV

[b00f]

Description

This PR updates the encryption logic to use Argon2-derived bytes for the Initialization Vector (IV) in AES, replacing the legacy approach of reusing the salt as the IV.

Explanation:

In the legacy or previous approach, we used the same salt in the Password Hasher (Argon2 in this case) as the Initialization Vector (IV) for the AES encryption algorithm. The seed is random and should not be an issue, but some documentation recommends never reusing a seed, even for different purposes.

To address this, we propose extending the key length from 32 bytes to 48 bytes, using the first 32 bytes as the encryption key and the remaining 16 bytes as the IV.

In OpenSSL, the salt is public. I found this code.
The encrypted files usually start with Salted__.

Based on this documentation, the IV is derived from the password in OpenSSL. Check the -iv section:

The actual IV to use: this must be represented as a string comprised only of hex digits. When only the key is specified using the -K option, the IV must explicitly be defined. When a password is being specified using one of the other options, the IV is generated from this password.

We follow the same approach in this PR. Here I found the code that generates IV in OpenSSL.

[codecov]

Codecov Report

Attention: Patch coverage is 86.04651% with 6 lines in your changes missing coverage. Please review.

Project coverage is 76.18%. Comparing base (86a8ba9) to head (b43284c).
Report is 57 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1703      +/-   ##
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+ Coverage   75.07%   76.18%   +1.10%     
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  Files         234      242       +8     
  Lines       12156    18668    +6512     
==========================================
+ Hits         9126    14222    +5096     
- Misses       2582     3983    +1401     
- Partials      448      463      +15     

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[Ja7ad]

I can't find recommended value for KeyLen and what is it keylen?

[b00f]

Check above explanation