Fix Firecracker PID resolution and deprecated net.Error.Temporary

Use context.Background() for resolveFirecrackerPID so a cancelled
request context (client disconnect) doesn't prevent tracking the
spawned Firecracker process, leaving it orphaned on cleanup.

Drop ne.Temporary() check in accept loop; deprecated since Go 1.18
and unreliable. Retry on any net.Error instead.

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

internal/daemon/daemon.go

@@ -168,7 +168,7 @@ func (d *Daemon) Serve(ctx context.Context) error {
 				return nil
 			default:
 			}
-			if ne, ok := err.(net.Error); ok && ne.Temporary() {
+			if _, ok := err.(net.Error); ok {
 				if d.logger != nil {
 					d.logger.Warn("daemon accept temporary failure", "error", err.Error())
 				}