fix(security): SSRF-guard node and remote HTTP clients

The Node.Probe and Remote.do paths built outbound URLs by string-
formatting admin-controlled fields (Scheme/Address/Port/BasePath)
straight into requests, then dialed the result with the default
transport. CodeQL flagged this as go/request-forgery — an admin
(or anyone who compromises the admin account) could point a node
at internal infrastructure (cloud metadata, RFC1918 ranges, etc.)
and the panel would dutifully fetch it.

Add util/netsafe with a shared TOCTOU-safe DialContext that
resolves the host, rejects private/internal IPs unless the
per-request context whitelists them (per-node AllowPrivateAddress
flag, plumbed through context.Value), and dials the resolved IP
directly so the IP that passed the check is the IP we connect to.
This closes the DNS-rebinding window where a hostname could
resolve to a public IP at check time and a private one at dial.

Also tighten address validation (NormalizeHost rejects anything
that isn't a bare hostname or IP literal — no embedded paths,
userinfo, schemes) and switch URL construction from fmt.Sprintf to
url.URL{} + net.JoinHostPort so admin-supplied values can't smuggle
URL components.

custom_geo.go's isBlockedIP now delegates to netsafe so there's
one source of truth.

web/service/custom_geo.go

@@ -18,6 +18,7 @@ import (
 	"github.com/mhsanaei/3x-ui/v3/database"
 	"github.com/mhsanaei/3x-ui/v3/database/model"
 	"github.com/mhsanaei/3x-ui/v3/logger"
+	"github.com/mhsanaei/3x-ui/v3/util/netsafe"
 )
 
 const (
@@ -164,8 +165,7 @@ func CustomGeoLocalFileNeedsRepair(path string) bool {
 }
 
 func isBlockedIP(ip net.IP) bool {
-	return ip.IsLoopback() || ip.IsPrivate() || ip.IsLinkLocalUnicast() ||
-		ip.IsLinkLocalMulticast() || ip.IsUnspecified()
+	return netsafe.IsBlockedIP(ip)
 }
 
 // checkSSRFDefault validates that the given host does not resolve to a private/internal IP.