🧹 [code health] Fix sed injection vulnerability in pre-install wizard

[WHYCRASH]

🎯 What: Added an escape_sed helper function to safely escape user inputs before passing them to sed commands in pre-install-wizard.sh.
💡 Why: Previous code allowed arbitrary sed command execution or script failure if user inputs contained backslashes, ampersands, or the specific delimiter used in the sed substitution command.
✅ Verification: Verified by a local testing script test_escape.sh that confirmed edge-case characters (e.g. |, /, \, &) are properly escaped. Confirmed script syntax with bash -n. Also underwent AI code review to ensure safety.
✨ Result: Improved security and robustness. The wizard is no longer susceptible to crashing or injection from malicious or accidental user input.

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PR created automatically by Jules for task 18427182745233172082 started by @WHYCRASH

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