Add RetosSwap and DawnSwap as Haveno network instances

[arnoldnakamura]

The current Haveno DEX entry links only to the base code repository. Haveno itself is a protocol — actual trading happens on network instances (similar to how Bisq has its own network).

This PR adds the two major running Haveno network instances:

• RetosSwap — The largest Haveno network with $2M+/month trading volume, 15% security deposits, and established arbitration (RoundTheRoses).
• DawnSwap — A newer network offering lower security deposits (5%), ~2% fees, and 24/7 arbitration. Growing user base.

Both are fully non-custodial, NO KYC, and use Tor automatically. They support Cash by Mail, Face-to-Face, bank transfer, and other payment methods for P2P cryptocurrency trading.

This is analogous to how the list includes both Bisq (the project) and its active network.