DecodeBase64ToUint decodes a Base64 string to a uint.

DecodeFromBase64 decodes a Base64-encoded string.

EncodeToBase64 encodes a string to Base64.

EncodeUintToBase64 encodes a uint to a Base64 string.

Hash generates a SHA-256 hash for the given string.

Save the uploaded file to the specified destination.

ValidateFileType checks if the file matches the expected type.