Serve full ISO for PXE boot via proxmox-iso-url kernel param

The Proxmox installer needs the full ISO to access packages and
installer data. Previously the ISO was deleted after extracting
kernel+initrd. Now we keep it as original.iso and serve it via HTTP.
The iPXE script passes proxmox-iso-url=<url> so the installer
fetches the ISO over the network instead of scanning block devices.

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

internal/image/service.go

@@ -55,6 +55,7 @@ func (s *Service) Upload(ctx context.Context, p UploadParams) (*model.Image, err
 
 	kernelPath := filepath.Join(p.Name, result.KernelFilename)
 	initrdPath := filepath.Join(p.Name, result.InitrdFilename)
+	isoPath := filepath.Join(p.Name, result.ISOFilename)
 
 	id, err := s.Store.Create(ctx, model.Image{
 		Name:       p.Name,
@@ -62,6 +63,7 @@ func (s *Service) Upload(ctx context.Context, p UploadParams) (*model.Image, err
 		Version:    p.Version,
 		KernelPath: kernelPath,
 		InitrdPath: initrdPath,
+		ISOPath:    isoPath,
 	})
 	if err != nil {
 		os.RemoveAll(destDir)