1. SSRF guard now blocks 0.0.0.0/8 (routes to localhost on Linux)
and 100.64.0.0/10 (CGNAT). Also rejects unspecified, multicast,
and loopback IPs via net.IP methods for defense in depth.
2. DNS monitor type no longer bypasses SSRF guard. The DNSServer
address is resolved and validated against isPrivateIP before use.
Port restricted to 53 — prevents arbitrary internal port probing
via crafted DNSServer values.
3. /metrics now default-deny when MetricsPublic is false, regardless
of whether UPTOP_CLUSTER_SECRET is set. Previously, no secret =
no auth check = metrics exposed to everyone.