refactor: extract interfaces to Interfaces folders and consolidate filters

Move interface declarations into per-area Interfaces/ subfolders, merge the
small task-list filter classes into StatusFilter/SmartFlagFilter, and simplify
related services, converters and hub DTO handling.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ClaudeDo.Releases/Interfaces/IReleaseClient.cs

@@ -0,0 +1,15 @@
+namespace ClaudeDo.Releases;
+
+public sealed record ReleaseAsset(string Name, string BrowserDownloadUrl, long Size);
+
+public sealed record GiteaRelease(
+    string TagName,
+    string Name,
+    IReadOnlyList<ReleaseAsset> Assets);
+
+public interface IReleaseClient
+{
+    Task<GiteaRelease?> GetLatestReleaseAsync(CancellationToken ct);
+
+    Task DownloadAsync(string url, string destPath, IProgress<long> progress, CancellationToken ct);
+}