🧹 Refactor do_GET to improve code health

[Ch3fUlrich]

🎯 What: The do_GET function in lib/linux/serve.py was too long and contained the logic for all GET endpoints directly within multiple if branches. This PR extracts each endpoint's logic into its own dedicated _handle_get_* method.
💡 Why: Splitting the routing logic into separate methods per endpoint improves code health by making each endpoint self-contained, greatly enhancing maintainability and readability, while simplifying the do_GET dispatcher down to an elegant URL router.
✅ Verification: I ran Python syntax checks via python3 -m py_compile lib/linux/serve.py and successfully executed the full Linux test suite (bash tests/run-tests.sh) to ensure no regressions were introduced.
✨ Result: A cleaner, more modular HTTP handler design that perfectly preserves all existing behavior.

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PR created automatically by Jules for task 14213116928302464281 started by @Ch3fUlrich

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