Beijing has warned the ruling party in Taiwan not to “mess up” Hong Kong affairs, as Taipei prepares to help Hongkongers seeking to flee their city, where a contentious national security law has been imposed.Zhu Fenglian, a spokeswoman for Beijing’s Taiwan Affairs Office, described the independence-leaning Democratic Progressive Party as a “black hand” that wanted to undermine the prosperity and stability of Hong Kong.“What the DPP authorities said was an undisguised distortion of facts, which…