WASHINGTON — Parkland father and activist Manuel Oliver wore the shoes his son Joaquin Oliver had planned to wear to prom to the White House on Monday as he attended President Joe Biden’s speech about new steps to curb gun violence. Oliver, an artist, was detained by police in February after staging a dramatic protest near the White House on the anniversary of the Parkland shooting. He scaled a construction crane and hung a banner with a picture of his son, one of the 17 people killed at Marjory Stoneman Douglas High School in 2018. The banner offered a critical message to Biden that “45k peop…