🔧 refactor: Use #!/usr/bin/env bash in all shell scripts (#16)

This commit refactors all the shell scripts to use `#!/usr/bin/env bash` instead of `#!/bin/bash`. This change ensures that the scripts will run with the system's default Bash interpreter, even if it is not located at the standard `/bin/bash` path.

download-zim-files/run.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 MESSAGE="Made by BigBearTechWorld"