appview/db: fix off-by-1 in punchcard

Date.YearDay produces an int in the range 1-365/366 but slices are
indexed from 0.

Signed-off-by: oppiliappan <[e-mail]>

appview/db/punchcard.go

···
 			punch.Count = int(count.Int64)
 		}
 
-		punchcard.Punches[punch.Date.YearDay()] = punch
+		punchcard.Punches[punch.Date.YearDay()-1] = punch
 		punchcard.Total += punch.Count
 	}