feat(hyperliquid): add stock symbol market data support

- Add Hyperliquid/XYZ symbol normalization tests and backend coverage

- Extend kline and market data lookup paths for US stock symbols

- Wire frontend data API types for stock-oriented market requests

api/handler_trader_symbol_test.go

@@ -0,0 +1,28 @@
+package api
+
+import "testing"
+
+func TestIsSupportedTraderSymbol(t *testing.T) {
+	tests := []struct {
+		name   string
+		symbol string
+		want   bool
+	}{
+		{name: "legacy USDT perp", symbol: "BTCUSDT", want: true},
+		{name: "legacy USDT perp lowercase", symbol: "ethusdt", want: true},
+		{name: "Hyperliquid xyz stock USDC pair", symbol: "SMSN-USDC", want: true},
+		{name: "Hyperliquid xyz commodity USDC pair", symbol: "GOLD-USDC", want: true},
+		{name: "legacy internal xyz prefix still accepted", symbol: "xyz:SMSN", want: true},
+		{name: "empty slot ignored", symbol: "  ", want: true},
+		{name: "bare stock without xyz prefix rejected", symbol: "SMSN", want: false},
+		{name: "unknown non-USDT pair rejected", symbol: "BTCUSD", want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := isSupportedTraderSymbol(tt.symbol); got != tt.want {
+				t.Fatalf("isSupportedTraderSymbol(%q) = %v, want %v", tt.symbol, got, tt.want)
+			}
+		})
+	}
+}