Fernando Mateo, the colorful co-founder of the prominent United Bodegas of America, angrily resigned Wednesday over the group’s president endorsing Zohran Mamdani for New York City mayor – calling it a “betrayal.” Mateo plans to hold a news conference Thursday morning denouncing the endorsement by president Radhames Rodriguez, whom he contended illegally violated the bodega owners’ group’s non-profit status by publicly backing a political candidate. “I did not agree with what was done today,” Mateo told The Post, adding that he was resigning “immediately.”