By Edwin Chan and Christina Farr SAN FRANCISCO (Reuters) – Apple Inc’s plan to pay $3.2 billion for Beats Electronics, which makes headphones and has an up-and-coming streaming music service, may herald a bolder use of its swelling cash pile and galvanize the iPhone maker’s move into wearables. Investors are still struggling to make sense of why CEO Tim Cook would break Apple’s decades-long tradition of relatively minor acquisitions of about $200 million to $400 million. Most observers say it’s going after a mix of technology and music industry talent in an effort to revive digital music …