🔒 Fix DoS vulnerability on read_line input handling in CLI helpers

[soniapi]

🎯 What: The vulnerability fixed
The unhandled Result responses on user stdin operations (such as .expect on read_line or .unwrap on stdout().flush()) were modified to use safe error handling (returning None or silently swallowing the flush error).

⚠️ Risk: The potential impact if left unfixed
Panicking directly on a bad user input stream or a closed output stream could lead to Denial of Service (DoS) situations where the application forcefully crashes upon encountering an IO failure.

🛡️ Solution: How the fix addresses the vulnerability
Replaced the panic-inducing calls with structured control flow. For read_line, a match statement handles an Err by gracefully returning None. For flush, the output is matched to safely ignore standard flush failure via let _ = ....

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PR created automatically by Jules for task 11507617284266801024 started by @soniapi

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