Add FollowRedirects option to downloader

Introduces a FollowRedirects property to UnitDownloaderOptions and its builder, allowing control over HTTP redirect behavior. Updates UnitDownloader to use this option, following redirects when enabled and reporting progress accordingly.

Beam.Downloaders/UnitDownloader.cs

@@ -25,8 +25,17 @@ namespace Beam.Downloaders {
 
         protected virtual async Task DownloadToStream(string url, int bufferSize, Stream destinationStream, IProgress<IDownloadReport> progress,
             CancellationToken ct) {
+            if (options.FollowRedirects) {
+                var response = await Client.GetAsync(url, ct); // automatically follows redirects
+                await response.Content.CopyToAsync(destinationStream, ct);
+                progress?.Report(new DownloadReport() {
+                    BytesDownloaded = destinationStream.Length,
+                    BytesRemaining = 0
+                });
+                return;
+            }
             
-            var stream = await Client.GetStreamAsync(url, ct);
+            var stream = await Client.GetStreamAsync(url, ct); // does not follow redirects
             byte[] buffer = new byte[bufferSize];
             int inBuffer = 0;
             long downloaded = 0;

Beam.Downloaders/UnitDownloaderOptions.cs

@@ -24,6 +24,8 @@ public record class UnitDownloaderOptions<OutType> {
     public string? DownloadFolder { get; init; } = null;
     public int BufferSize { get; init; } = 80 * 1024; // 80kb
 
+    public bool FollowRedirects { get; init; } = true;
+
     public string GetFileNameForDownload(string url, byte[] additionalData) {
         byte[] bytes = [..Encoding.UTF8.GetBytes(url), ..additionalData];
         var name = Convert.ToBase64String(System.IO.Hashing.XxHash64.Hash(bytes));

Beam.Downloaders/UnitDownloaderOptionsBuilder.cs

@@ -13,12 +13,18 @@ public sealed class UnitDownloaderOptionsBuilder<OutType> {
     private AsyncTransformer<ByteDocument, OutType>? _asyncTransformer;
     private string? _downloadFolder = null;
     private int _bufferSize = 80 * 1024;
+    private bool _followRedirects = true;
 
     public UnitDownloaderOptionsBuilder<OutType> WithTarget(DownloadTarget target) {
         _target = target;
         return this;
     }
 
+    public UnitDownloaderOptionsBuilder<OutType> WithFollowRedirects(bool followRedirects) {
+        _followRedirects = followRedirects;
+        return this;
+    }
+        
     public UnitDownloaderOptionsBuilder<OutType> WithClient(HttpClient client)
     {
         _client = client ?? throw new System.ArgumentNullException(nameof(client));
@@ -98,6 +104,7 @@ public sealed class UnitDownloaderOptionsBuilder<OutType> {
             Client = _client,
             FailurePredicateOptions = _failurePredicateOptionsOverride,
             SkipPredicateOptions = _skipPredicateOptionsOverride,
+            FollowRedirects = _followRedirects,
             FragmentOptions = _fragmentOptions,
             AsyncTransformer = _asyncTransformer,
             DownloadFolder = _downloadFolder,