Function decrypt_file_with_cache 

pub fn decrypt_file_with_cache(
    path: &Path,
    key_cache: &DashMap<[u8; 16], Arc<OnceLock<Result<Zeroizing<[u8; 32]>, String>>>>,
    cache: Option<CacheRef<'_>>,
    master_key: &[u8],
) -> Result<()>

Decrypt a single file with a thread-safe Argon2 key cache and optional salt/file_id cache.