Expose complete Proxy connectivity topology and registration gaps

### Problem\n\nThe Proxy page calls the live topology endpoint but currently reduces each result to a single status. Operators cannot inspect gRPC and Remoting reachability, probe latency, port assignments, host concentration, or nodes that differ between the registered address list and discovery results.\n\n### Proposed solution\n\nAdd a connectivity topology inventory that correlates registered addresses with live probe records and provides:\n\n- per-node gRPC and Remoting ports and reachability;\n- probe latency and current-node context;\n- explicit registered-only and discovered-only states;\n- host distribution and port summaries;\n- status/text/gap filters and CSV export.\n\nThe feature uses the existing endpoints and does not change Proxy registration or configuration behavior.

Start at the Proxy page and trace its call to the live topology endpoint, then inspect how registered addresses and discovery results are represented. The work is done when the page exposes per-node gRPC and Remoting reachability, ports, latency, current-node context, registration gaps, summaries, filters, and CSV export without changing Proxy registration or configuration behavior.

Written by the indexing model from the issue text.