refactor(mcp-common): centralize base_url defaults in resolve_environment

Aggiunti kwargs opzionali default_base_url_live / default_base_url_testnet
a resolve_environment. Rimosse 8 chiamate creds.setdefault duplicate dai
4 servizi (alpaca, bybit, deribit, hyperliquid) ora passano gli URL
canonici direttamente al resolver.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

services/mcp-hyperliquid/src/mcp_hyperliquid/__main__.py

@@ -19,14 +19,13 @@ def main():
     with open(wallet_file) as f:
         creds = json.load(f)
 
-    creds.setdefault("base_url_live", "https://api.hyperliquid.xyz")
-    creds.setdefault("base_url_testnet", "https://api.hyperliquid-testnet.xyz")
-
     env_info = resolve_environment(
         creds,
         env_var="HYPERLIQUID_TESTNET",
         flag_key="testnet",
         exchange="hyperliquid",
+        default_base_url_live="https://api.hyperliquid.xyz",
+        default_base_url_testnet="https://api.hyperliquid-testnet.xyz",
     )
 
     client = HyperliquidClient(