A sniper has assassinated Adnan Hussein, the mayor of Fallujah, and several attacks have killed police officers at their checkpoints, offices and homes throughout the city – the latest violence in a major al-Qaida offensive that has plunged Anbar province into a worsening security crisis.In the past four weeks, al-Qaida-affiliated militants have launched an intense wave of attacks on government buildings, security forces, and civilians, both in the remote desert along the Syrian border an…