WASHINGTON — President Barack Obama’s health-care law is enmeshed in another big legal battle after two federal appeals courts today issued contradictory rulings on a key financing issue within hours of each other. A divided court panel in Washington called into question the subsidies that help millions of low- and middle-income people pay their premiums, saying financial aid can be paid only in states that have set up their own insurance markets, or exchanges. About 100 miles to the south in Richmond …