fix(hyperliquid): stop SDK init panic from crashing trader creation with 500

go-hyperliquid's NewExchange auto-fetches meta/spotMeta/perpDexs and
panics if any of those API calls fail (NewInfo: panic(err)). The quick
trade flow constructs a probe trader inside POST /api/traders, so any
transient Hyperliquid API hiccup crashed the request with a recovered
panic and a bare 500. Wrap the constructor in initExchangeClient, which
converts the panic into an error that surfaces through the existing
exchange-probe validation path as an honest, retryable message.

trader/hyperliquid/client_init.go

@@ -0,0 +1,22 @@
+package hyperliquid
+
+import (
+	"fmt"
+
+	hl "github.com/sonirico/go-hyperliquid"
+)
+
+// initExchangeClient runs the SDK exchange constructor and converts its
+// panic-on-failure behavior into an error. go-hyperliquid's NewExchange
+// auto-fetches meta/spotMeta/perpDexs when they are passed as nil and panics
+// if any of those API calls fail (NewInfo: panic(err)), so a transient
+// Hyperliquid API hiccup would otherwise crash the calling HTTP handler
+// with a 500.
+func initExchangeClient(build func() *hl.Exchange) (ex *hl.Exchange, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("hyperliquid client initialization failed: %v", r)
+		}
+	}()
+	return build(), nil
+}