Add Cardano (ADA) support for trading and funding accounts

Enable Cardano (ADA) as a supported asset for both funding (deposits/withdrawals) and spot trading. Use case: allow users who hold ADA to fund accounts, withdraw ADA, and trade ADA against fiat and other crypto to increase user acquisition and trading volume. Expected behavior: users can view ADA balances in wallets and portfolio, deposit ADA with network-specific deposit addresses and clear confirmations, withdraw ADA with fee estimation and network status, and place/cancel orders for ADA trading pairs (e.g., ADA/USD, ADA/BTC) via existing order types. Backend requirements include wallet custody or third-party node integration, address and transaction monitoring, confirmation requirements, fee handling, and AML/KYC and risk checks consistent with other supported assets. Frontend requirements include UI for ADA deposits/withdrawals, trading pair listings, price/market data, order entry, trade history, and appropriate error/notification handling for network issues and insufficient confirmations.