feat: dash support

[frolvanya]

near (testnet) -> dash (mainnet)
init https://testnet.nearblocks.io/txns/9F68S4QH2UCs2mrEJRbDXbNpKDhJMbvj66bbnhBXnfmm
sign https://testnet.nearblocks.io/txns/7PWrPwe1bxtt4ABZEsKfVzWAnu7vZ3tKqWEu1eGA5YC
fin https://insight.dash.org/insight/tx/5dc37febd3c22489f4e8b3c782a6cc59d1c1b5f14138091d69759231aad79769

I've tested on dash mainnet, because I couldn't find a working faucet on testnet

[Copilot]

Pull request overview

Adds a new dash feature/variant to the satoshi-bridge contract, introducing DASH address support and switching DASH transaction verification from the BTC light client to NEAR MPC verify_foreign_transaction.

Changes:

• Add dash as a build feature/variant (Makefile + contract reproducible build metadata).
• Extend network::Chain with Dash mainnet/testnet and implement address prefix handling.
• Add DASH-specific transaction/PSBT utilities and an MPC-based verification module; wire verification callbacks to support both light-client (non-dash) and MPC (dash).

Reviewed changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Makefile	Adds dash to build/lint/test feature matrix.
contracts/satoshi-bridge/Cargo.toml	Adds reproducible-build variant for dash and a dash feature flag.
contracts/satoshi-bridge/src/lib.rs	Adds dash_utils + mpc_verifier modules and switches re-exports under dash feature.
contracts/satoshi-bridge/src/network.rs	Adds DashMainnet/DashTestnet and corresponding address prefix/SegWit HRP handling + tests.
contracts/satoshi-bridge/src/mpc_verifier.rs	New module to call MPC verify_foreign_transaction for DASH tx verification.
contracts/satoshi-bridge/src/btc_light_client/mod.rs	Introduces shared assert_verification_succeeded() to handle light-client vs MPC verification results.
contracts/satoshi-bridge/src/btc_light_client/{deposit,withdraw,active_utxo_management}.rs	Switches verification promise construction to MPC under dash and uses shared callback assertion.
contracts/satoshi-bridge/src/dash_utils/*	New DASH-specific transaction wrapper, PSBT wrapper, contract-method shims, and chain-specific types.
contracts/satoshi-bridge/src/utils.rs	Adds MAX size constant for MPC verification result under dash.
contracts/satoshi-bridge/src/unit/mod.rs	Updates unit test chain selection to include dash.
Cargo.lock	Large dependency graph changes.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[frolvanya]

we need to parse response properly, I left it as todo for now