Add a check for stream keys in scripts/validate.sh

[TonkaToyXL]

Updated scripts/validate.sh to include a validation check for stream keys (e.g., live_[0-9]+_[a-zA-Z0-9]+), ensuring they are not accidentally committed. This aligns with the guidelines in FOR-US.md and SECURITY.md.

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PR created automatically by Jules for task 8488391899493015548 started by @TonkaToyXL

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