Add spot sell retry UI; sell all trading-account coin on sell-back.

Fix coin-margin sell-back to use full available balance instead of bridge record; show retry banner and button on the options positions panel.

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

lib/sim/hooks.py

@@ -468,14 +468,11 @@ def _patch_spot_bridge_lib() -> None:
         try:
             if _GET_DB is not None and is_sim_mode(_GET_DB):
                 coin = (underlying or "ETH").strip().upper() or "ETH"
-                amt = coin_amount
-                if amt is None or float(amt) <= 0:
-                    amt = fetch_trading_coin_available(ex, coin)
-                    if amt is None or float(amt) <= 0:
-                        return {"ok": False, "msg": f"交易账户无可用 {coin}"}
-                sell_sz = float(amt)
-                if sell_sz > 1e-8:
-                    sell_sz = max(0.0, sell_sz * 0.999)
+                _ = coin_amount
+                avail = fetch_trading_coin_available(ex, coin)
+                if avail is None or float(avail) <= 0:
+                    return {"ok": False, "msg": f"交易账户无可用 {coin}"}
+                sell_sz = max(0.0, float(avail) * 0.999)
                 if sell_sz <= 0:
                     return {"ok": False, "msg": f"{coin} 可卖数量过小"}
                 pub = _sim_public_exchange(ex)