MECHANICVILLE, N.Y. — Wednesday night was bittersweet for Mechanicville High School boys’ soccer senior Graham Murphy. Sweet because his team defeated Hudson Falls 5-1 in the first round of the Section 2 Class B playoff tournament. Bitter (as much as you can be after a postseason victory) because it might be the last time he takes the home pitch in the red, black and white kit. As Murphy looked across the lit field after the win, memories rushed…