New "CRYPTO" value on the exchange enum

Trading API

Adds CRYPTO to the exchange enum. Crypto assets like BTC and ETH now report CRYPTO as their exchange across asset, position, and watchlist responses.

Affected Endpoints

• GET /v2/assets
• GET /v2/assets/{symbol_or_asset_id}
• GET /v2/positions
• GET /v2/positions/{symbol_or_asset_id}
• POST /v2/watchlists
• GET /v2/watchlists/{watchlist_id}
• POST /v2/watchlists/{watchlist_id}
• PUT /v2/watchlists/{watchlist_id}
• DELETE /v2/watchlists/{watchlist_id}/{symbol}
• GET /v2/watchlists:by_name
• POST /v2/watchlists:by_name
• PUT /v2/watchlists:by_name