fix(ssh): close zombie local port forwarder on SSH keep-alive ping failures

[ZhuchkaTriplesix]

Closes #1374

Summary

• Tracks consecutive keep-alive ping failures (max 2) in SshTunnelManager's keepAliveTimer.
• Proactively cleans up zombie sessions by closing the local ServerSocket and SSHClient and evicting the session from the pool map.
• Ensures subsequent connection requests to the pool key establish a clean new SSH tunnel rather than reusing a dead forwarder.
• Added unit tests covering consecutive ping failures, eviction/listener cleanup, and transient single-failure recovery.