Improve station connectivity diagnostics

Faster troubleshooting when the kiosk page is unreachable or blank, with clearer log output pointing at the actual cause.

• Added tofupilot service status loopback probe that reports listening, refused, or timeout, and names the process holding the port.
• Added locale-stable Windows port-holder lookup so non-English Windows hosts (Chinese, Japanese, German, French) report the same diagnostics as macOS and Linux.
• Fixed hardcoded port 7321 in several paths so TOFUPILOT_LOCAL_UI_PORT is honored everywhere.
• Improved bind errors with specific remediation hints for port-in-use, permissions, loopback down, and container/network-namespace cases.
• Added kiosk readiness probe and browser exit detection so blank-page situations surface in the logs instead of failing silently.