Proxy support for SNMP, CLI, ICMP, and REST API device communication

NetBrain currently requires direct network connectivity to managed devices for SNMP, CLI, ICMP, and REST API access, with no supported mechanism to route these protocols through an intermediary proxy. This enhancement would add configurable proxy support for each of these access methods, allowing NetBrain to reach devices in environments where direct connections are restricted or unavailable. Customers operating in segmented or security-restricted network environments would benefit from broader device visibility and management without requiring architectural changes to their existing access controls.