Allow for cancelling downloads from filesystem

Rebuild request orignally will use setting for constructing the url
Rebuild request from client via no-cache will use httppcontext to get runtime pathing to generate url
Escape the url generated

TinfoilVibeServer/Services/SnapshotService.cs

@@ -649,7 +649,7 @@ public sealed class SnapshotService : IDisposable, ISnapshotService, IHostedServ
 
     public class ROMSnapshot
     {
-        public string Hash { get; set; }
+        public string? Hash { get; set; }
         public IReadOnlyList<FileEntry> Files { get; set; } = new List<FileEntry>();
     }
 
@@ -664,8 +664,9 @@ public sealed class SnapshotService : IDisposable, ISnapshotService, IHostedServ
         new Timer(_ => DebounceElapsed(), null, Timeout.Infinite, Timeout.Infinite);
     }
 
-    public async Task StopAsync(CancellationToken cancellationToken)
+    public Task StopAsync(CancellationToken cancellationToken)
     {
         Dispose();
+        return Task.CompletedTask;
     }
 }