Add license to Harbor examples

[qgallouedec]

#6018 merged before applying the pre-commit (make precommit)

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Note

Low Risk
Comment-only license headers; no logic or configuration changes.

Overview
Adds the standard Hugging Face Apache 2.0 copyright header to kernel_server.py and run_cell.py under the Harbor Jupyter harness—files that landed without it when related Harbor work merged before make precommit ran.

No runtime or API behavior changes; this only aligns those two scripts with the rest of the Harbor examples.

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[bot-ci-comment]

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