fix(okx): import os in options lib so OKX app can start

Tickers cache TTL used os.getenv without importing os, crashing crypto_okx on boot after deploy.

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/exchange/okx_options_lib.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 
 import json
 import math
+import os
 import re
 import threading
 import time