This change modifies the `clusterEndpointEffectiveURL` function to prioritize
IP addresses over hostnames when building cluster endpoint URLs. This eliminates
excessive DNS lookups that can overwhelm DNS servers (e.g., pi-hole), which was
causing hundreds of thousands of unnecessary DNS queries.
When Pulse communicates with Proxmox cluster nodes, it will now:
1. First try to use the IP address from ClusterEndpoint.IP
2. Fall back to ClusterEndpoint.Host only if IP is not available
This is a minimal, backwards-compatible change that maintains existing
functionality while dramatically reducing DNS traffic for clusters where
node IPs are already known and stored.
Related to #620
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