Harden env save against empty numerics; default coin margin and hedge off.

Reject blank float/int/select on save and parse env with safe helpers so options config edits cannot crash into 502; default OKX_TRADE_MODE=options and OKX_OPTIONS_MARGIN_MODE=coin.

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

lib/options/options_register.py

@@ -34,9 +34,9 @@ def _env_bool(key: str, default: bool = False) -> bool:
 
 def _env_float(key: str, default: float) -> float:
     try:
-        return float(os.getenv(key, str(default)))
+        return float(os.getenv(key) or default)
     except (TypeError, ValueError):
-        return default
+        return float(default)
 
 
 def attach_options_templates(app: Flask, repo_root: str) -> None: