President Obama has kept his vow to wind down two wars and bring home troops — but meeting the job, educational and medical needs of those returning veterans also has become a challenging priority for the White House. Mr. Obama made veterans’ care a major theme during the 2008 campaign. Since taking office, Mr. Obama has embraced a broad program of tax credits to spur hiring of veterans and approved record budgets to bolster health care for those who served in Iraq and Afghanistan.