Key developments on April 4: Russian double-tap attack on Kharkiv kills 4, including first respondersSBU: Russian forces used cyberattack to target Ukraine’s 128th brigadeGerman FM says Berlin will initiate search for more air defense for UkraineEnergoatom: Zaporizhzhia nuclear plant ‘on verge of blackout’ after recent Russian attackPoll: Fewer than 50% of Ukrainians believe war will end with restoration of 1991 borders.Two Russian strikes on the city of Kharkiv killed four people, including three first responders, and injured 12, Kharkiv Oblast Governor Oleh Syniehubov said in the early hours…