SAN FRANCISCO — The tech industry has long prided itself on its many immigrant founders, executives and software programmers. Now, fears are growing among foreign tech workers that their lives and careers may be upended by the Trump administration’s more stringent immigration policies.Tech companies are telling employees on visas not to leave the United States out of concern they might not be allowed back in. Law firms are warning that denial rates for high-skilled visas could rise, as they did ...