Add ShellCheck compliance to all hook scripts

[VictorVVedtion]

Run shellcheck hooks/*.sh and fix any warnings or errors. The CI workflow already includes ShellCheck, so this ensures all hooks pass.

Scope: hooks/*.sh
Skills: Bash scripting
Difficulty: Easy

[aehliglucas]

Hi! There are no warnings or errors when running shellcheck over the .sh files in hooks/. You should be good. :)