Federal immigration officials said Thursday that they have deported a man to the Czech Republic after holding him for more than seven years, making him the longest-held detainee in America never charged with any crime. Immigration and Customs Enforcement had said that Scott Vitkovic was a danger to public safety who delayed his own deportation by refusing to cooperate with them. The FBI said Vitkovic had worn an Osama bin Laden T-shirt to a Cambridge mosque and told some members that he wanted to attack the United States. Vitkovic acknowledged wearing the shirt, but denied making the statements and pointed out that federal officials never charged him with a crime. He had been held in the Suffolk County House of Correction.