feat(cluster): preserve isolated replication over gRPC

[yordis]

• Preserves isolated replication topology and failure detection on the supported gRPC transport.

[cursor]

PR Summary

High Risk
Changes core cluster membership, gossip serialization, and replication listener isolation—security- and availability-critical paths—with a breaking shift away from TCP endpoints in the node model.

Overview
This PR replaces the old internal/external TCP cluster model with HTTP for client/admin traffic and a dedicated HTTP/2 listener for gRPC replication, including gossip that carries a separate ReplicationEndPoint (falling back to HTTP when absent for mixed-version clusters).

Runtime wiring: Kestrel now listens on both node and replication addresses; ReplicationEndpointPolicy returns 404 unless replication traffic hits the replication listener on the replication service path (and blocks that path on the main node port). NodeConnectionTracker wraps connections to record bytes, TLS, and HTTP vs gRPC usage for operator visibility. The cluster UI and replica status logic drop TCP columns and match replicas by HTTP endpoint instead of internal TCP.

Configuration & API cleanup: Adds ReplicationPortAdvertiseAs (with deprecated alias compatibility), validates that node and replication listeners cannot overlap on the same address/port, and simplifies leader advertisement to HTTP only (including NotHandled leader info and forwarding tests).

Tests: Removes the TCP unit-test plugin, legacy ClientAPI TCP helpers, and TCP transport tests; cluster/integration coverage moves to gRPC streams and updated mini-node fixtures with node + replication endpoints.

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