Add upload progress bar with SSE extraction status

ISO uploads now show a progress bar during file transfer (via XHR
upload.onprogress) and real-time extraction status (via SSE events
through the existing Hub). Falls back to plain form POST if JS is
disabled.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/image/service.go

@@ -18,10 +18,11 @@ type Service struct {
 }
 
 type UploadParams struct {
-	Name    string
-	Kind    string
-	Version string
-	ISO     io.Reader
+	Name       string
+	Kind       string
+	Version    string
+	ISO        io.Reader
+	OnProgress ProgressFunc
 }
 
 var slugRegex = regexp.MustCompile(`^[a-z0-9][a-z0-9.-]*$`)
@@ -46,7 +47,7 @@ func (s *Service) Upload(ctx context.Context, p UploadParams) (*model.Image, err
 		return nil, fmt.Errorf("create image dir: %w", err)
 	}
 
-	result, err := ExtractFromISO(p.ISO, destDir)
+	result, err := ExtractFromISOWithProgress(p.ISO, destDir, p.OnProgress)
 	if err != nil {
 		os.RemoveAll(destDir)
 		return nil, fmt.Errorf("extract ISO: %w", err)