feat(rust/hermes-ipfs): ipfs persistent keypair

[cong-or]

Add with_keypair() Method to HermesIpfsBuilder for Persistent Keypair Support

Summary

This PR adds a with_keypair() method to HermesIpfsBuilder that enables creating an IPFS
node builder with an existing keypair instead of auto-generating a new one. This is
essential for supporting persistent peer identities across node restarts.

Motivation

Currently, hermes-ipfs only exposes HermesIpfsBuilder::new(), which auto-generates a new
keypair on each instantiation. While the underlying rust_ipfs::IpfsBuilder supports
creating builders with existing keypairs via IpfsBuilder::with_keypair(), this
functionality was not exposed through the hermes-ipfs API.

Without this capability, applications cannot:

• Maintain stable peer IDs across restarts
• Load keypairs from persistent storage
• Use deterministic peer identities for testing or deployment

Changes

Added HermesIpfsBuilder::with_keypair() method

pub fn with_keypair(keypair: impl connexa::builder::IntoKeypair) ->
    std::io::Result<Self>

• Accepts any type implementing connexa::builder::IntoKeypair (including
  libp2p::identity::Keypair)
• Wraps the underlying IpfsBuilder::with_keypair() method

Usage Example

use hermes_ipfs::HermesIpfsBuilder;
use libp2p::identity::Keypair;

// Load a keypair from disk (or generate and save)
let keypair = load_or_create_keypair("path/to/keypair.key")?;

// Create builder with the persistent keypair
let node = HermesIpfsBuilder::with_keypair(keypair)?
    .with_default()
    .set_default_listener()
    .enable_tcp()
    .enable_quic()
    .enable_dns()
    .start()
    .await?;

// Node will now have the same peer ID on every restart

[github-actions]

📚 Docs Preview

The docs for this PR can be previewed at the following URL:

https://docs.dev.projectcatalyst.io/libs/feat/hermes-ipfs-persistent-keypair

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 605/605}$ | ${\color{red}Fail: 0/605}$ |

[rafal-ch]

LGTM 👍