Remove USDC product path; CoinOX is coin-margined only.

Drop USDC open/quote/swap APIs and env knobs; retarget hedge/settings copy to USDT/coin.

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

lib/options/options_margin_mode_lib.py

@@ -53,9 +53,8 @@ def margin_mode_from_inst_id(inst_id: str) -> str:
 
 
 def premium_ccy_for_mode(margin_mode: str, underlying: str = "ETH") -> str:
-    if normalize_options_margin_mode(margin_mode) == MODE_COIN:
-        return (underlying or "ETH").strip().upper() or "ETH"
-    return "USDC"
+    """CoinOX 仅币本位:权利金币种为标的币."""
+    return (underlying or "ETH").strip().upper() or "ETH"
 
 
 def spot_quote_inst_id(underlying: str) -> str:

lib/options/templates/options_settings_transfer.html

@@ -4,8 +4,9 @@
         <input type="text" name="username" autocomplete="username" tabindex="-1" aria-hidden="true"
                style="position:absolute;left:-9999px;width:1px;height:1px;opacity:0" value="">
         <select id="opt-set-int-ccy" aria-label="币种" autocomplete="off">
-            <option value="USDC" selected>USDC</option>
-            <option value="USDT">USDT</option>
+            <option value="USDT" selected>USDT</option>
+            <option value="ETH">ETH</option>
+            <option value="BTC">BTC</option>
         </select>
         <select id="opt-set-int-from" aria-label="划出账户">
             <option value="funding" selected>from: 资金</option>