fix: full arb table + net profit columns in price view

- ArbTable: removed slice(0,10) cap, shows all 42 opps (21x2)
- PriceTable: added net_bg_to_hl and net_hl_to_bg columns
- Backend SSE: sends net profit for both directions per coin

exchange/bitget_trade.go

@@ -42,6 +42,7 @@ func (b *BitgetTrade) PlaceMarketOrder(side, symbol, size, tradeSide string) (st
 	body := map[string]interface{}{
 		"marginCoin":  "USDT",
 		"symbol":      symbol,
+		"productType": "USDT-FUTURES",
 		"side":        side,
 		"orderType":   "market",
 		"timeInForce": "IOC",