The tech-savvy model in the mainland’s emerging self-storage industry is leaving Hong Kong’s sector behind, according to two pioneers in the trade across the border.The industry in space-starved Hong Kong took off a decade earlier, and facilities in the city still outnumber the total on the mainland. But the two industry leaders, who are from Hong Kong but based in Beijing and Guangzhou, said the city’s industry was behind in terms of technology development.“You still need a key to open locks…