chore(test): replace netcat with Python HTTP server in network tests

[dobrac]

Note

Low Risk
Test-only changes that swap the header-capture mechanism; no production code or security-sensitive logic is modified.

Overview
Updates the JS SDK and Python SDK network tests for maskRequestHost to stop installing/using netcat to capture inbound headers.

The tests now launch a lightweight Python http.server handler that writes received request headers to /tmp/headers.txt, then read that file to assert the masked Host value; related waits/timeouts and command options were adjusted to match the new approach.

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Latest commit: a6992a6

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