Function presign_get_object 

pub async fn presign_get_object(
    client: &Client,
    bucket: &str,
    key: &str,
    expires_secs: u64,
) -> Result<PresignedUrl, AppError>

Generate a presigned GetObject URL for bucket/key.

Arguments

• client — AWS S3 client (already scoped to the correct region/profile).
• bucket — Bucket name.
• key — Full object key.
• expires_secs — URL lifetime in seconds. Must be in [60, 604_800].

Errors

• AppError::Validation { field: "expires_secs", … } when expires_secs is outside the allowed range.
• AppError::Internal { … } when the AWS SDK presigning call fails.