Chicago Mayor Brandon Johnson began his first term of office Monday, asking Chicagoans to set aside deep differences, confront challenges together and build “a city that works for everyone.” Johnson, 47, whose victory was touted by progressives as evidence that bold stances lead to victory, must immediately confront an influx of migrants in desperate need of shelter, pressure to build support among skeptical business leaders, and summer months that historically bring a spike in violent crime. His first term leading the …