Use email and calendar history in Shuffle

Shuffle builds each card from what's saved on the contact in Dex and the most recent message on each connected channel. It doesn't use email or calendar history, so for contacts you mostly email or meet with, the card has little to say about why they came up.

Request: draw on connected email and calendar history (past meetings, recent threads, how you met) when explaining why a contact surfaced and suggesting what to say.