修复一些已知问题，优化V6路由分配

backend/internal/api/request.go

@@ -0,0 +1,15 @@
+package api
+
+import (
+	"net"
+	"net/http"
+	"strings"
+)
+
+func clientIP(r *http.Request) string {
+	host, _, err := net.SplitHostPort(strings.TrimSpace(r.RemoteAddr))
+	if err == nil {
+		return host
+	}
+	return strings.TrimSpace(r.RemoteAddr)
+}